But, you think, it feels so brutal to tell them what the adult realists among us may know for months or years, that Mom or Dad has metastatic disease or a type of cancer that almost always kills.
Read a little further and you find that some of the experts don't think you should be that honest.
"This does not mean that parents should tell their kids everything they know as soon as they know it," cautions the American Cancer Society.
As the NIH concedes, this leaves parents seeking a delicate balance between "avoidance and confrontation."
It also can leave them feeling guilty, frightened, and utterly unprepared to perform one of the most difficult jobs a parent can face.
"It's always hard. It's hard to say, 'This is an illness people have died from and we're hopeful.' Even that is hard. Everybody struggles with that," said Grace Christ, a children's bereavement expert at Columbia University who wrote Healing Children's Grief. "I think even the research centers don't do enough to help families."
People who work with families coping during the illness and after a parent dies say more effective treatments have made deciding what to tell children and when to say it even more difficult. Some cancers still kill almost everyone they strike, but it's harder to guess when the deaths will occur.
Some experts still say it's better to let children, especially older ones, in on the secret quickly. Some say most people wait until a parent is entering hospice, and that's about right. Others say to dribble out the bad news over time while answering questions as truthfully as possible.
Basically, there are so many variables - the parent's specific illness and coping style, the children's ages and coping styles - that there are no simple answers.
Phyllis Silverman, an expert on children and grief who wrote Never Too Young to Know: Death in Children's Lives, recommends telling kids early. Now 84 and a scholar in residence at Brandeis University, she is undergoing treatment for recurrence of a treatable form of lung cancer and has told her grandchildren about it.
Parents may think they're protecting children from life's hardest lessons, but Silverman thinks kids benefit from learning they can "master some of the vicissitudes of living. . . . Kids can take it. Kids can handle things better than you think, as long as they know they have you to count on."
Wendy Harpham, a Texas doctor and 21-year non-Hodgkins lymphoma survivor, thinks it's OK not to bring up death if a parent is functional and still undergoing treatment, but she was more open with her own children.
Before bed one night, her then-8-year-old daughter asked if she would live to celebrate her bat mitzvah. "I am going to die," Harpham told her. "I may die of cancer. The treatment I'm getting makes me hope." She added that, if she didn't make it to the bat mitzvah, 'You will feel my love, and it will be a happy, joyous time.' I provided an answer she could live with, and she immediately relaxed and fell asleep." Harpham went into the next room and cried.
Harpham, who has lived well past the bat mitzvah, thinks there's a price for hiding the truth. "Whether you mean to or not, a parent who doesn't include the child is saying, 'I don't respect you, and I don't think you can handle the truth.' . . . The greatest gift that we can give our children is not protection from the world, but the confidence and tools to cope and grow with all that life can offer."
Christ, the Columbia bereavement expert, thinks parents should talk with children early and often. The message changes as the disease progresses.
"There are times when death is possible, but not probable," she said. "There are times when it's probable. There are times when it's inevitable, and there are times when it's imminent."
There's no point in inundating young children with information they can't understand, she said. They just need a sense that the family will get through this together.
Teenagers can understand, but need help managing intense emotions. A parent can talk to them about opening up with a counselor, telling their friends, building a support network, having the conversations they want to have with the sick parent, and using music and writing as an outlet.
Experts agree that parents should always explain symptoms the kids can see or the side effects of treatments.
Jennifer Singer, coordinator of the David Bradley Children's Bereavement Program for Penn Wissahickon Hospice, says children need to hear about the impending death from a parent, but the disclosure doesn't have to be far in advance. "Especially for young children to know for a year or two that their parent is going to die, that's just too long," she said. "I think for any child to know for a year or two is too long."
Parents can say that some people, maybe even many or most people, die from this particular kind of cancer, but they don't know what will happen this time. "It's not a lie to say we don't know because, really, we don't know."
Kathleen Coyne, program director at Cancer Support Community of Philadelphia, said children can be informed honestly without talking about prognosis. They can be told that Mom's breast cancer has spread to her bones or that you hope the latest treatment will keep the cancer at bay. Don't use the word "cure." Tell them, "When the situation changes, I'll be sure to let you know."
Leave the door open for questions or ask if they're worried. An information vacuum only feeds their imaginations, Coyne said. Address what they see in the healthy parent as well as the sick one. You can start a conversation by saying, "You're probably aware of the fact that you've seen me cry three times this week."
Kathleen McCue, director of children's programming at the Gathering Place in Beachwood, Ohio, and author of How to Help Children Through a Parent's Serious Illness, used to think parents should be honest with the kids about everything from the start. She says she and other experts she knows have mellowed on this. To maintain a child's trust, she cautions against saying either that Daddy will die by a particular time or that he will be cured. Other than that, she's come to believe that parents know their children best and can be trusted to figure out the best timing.
Because they lack a good sense of time, young children don't understand what it means that someone is going to die. "They think they're going to die now, right then," McCue said.
They're also very concrete, so be careful about saying things such as "Daddy's going to heaven." Some think heaven is like a town Daddy could visit and come home from.
As a parent's symptoms become more noticeable, McCue said, children can be told, "When people get sicker from this disease . . . what usually happens is they die, but we never know when they're going to die. . . . What we need to do as a family is make the very most of those days or weeks or months knowing that our time isn't unlimited."
When death is close, make sure the kids have a last chance to say, "I love you." That's when to say, "If there is anything you haven't done or said, this is the time to do it."
Carrie Miluski, executive director of Peter's Place, which helps grieving children, said kids come down on both sides after a parent dies. Some are glad they knew all along that things were dire. Others say, "If I'd known the whole time, it would have made the year unbearable for me."
How much any of this matters over the child's lifetime has not been studied adequately. Kids who lose a parent have fewer mental health problems than popular culture would lead us to believe, but they are at higher risk than kids in intact families. One key factor in how they recover from the death - and here's more pressure for parents - is how the surviving parent responds.
"The reaction and coping of the surviving parent or caregiver is often one of the most important predictors of how the child will do," Singer said.
It's OK for children to see that the healthy parent is upset, but "what we don't want children to feel is that they have to be the ones to take care of the emotional needs of their parent," she said. It's especially important that parents seek the support they need, even though it can be hard to find before the death. "I can't say enough how much modeling is at play here," she said.
Even if you don't do everything perfectly during the illness, you can still repair relationships afterward.
"In the end, as parents we're all just learning this as we're going along, and kids are more resilient than we give them credit for," Coyne said. Parents can say, "I'm grieving. I'm sad. I'm lonely. I can do all that and still be your mom."
Understanding Child Development - and How to Talk With Kids About Death
Very young children do not understand the permanence of death or cause and effect. They may ask for weeks or months whether a dead parent will return.
They're especially concerned about separation from a primary caregiver.
Anticipate that the child needs reassurance he or she will be cared for.
Children this age need consistent substitute caregivers.
Use play and art to explain what's going on.
Children 6 to 8 years old understand a dead parent will not come back but may worry that their thoughts or words caused the illness or death. Explain changes in a parent's behavior or function that a child sees. Tell the child it's all right to ask questions and express strong emotions.
Those 9 to 11 need detailed information about the illness and treatment. Name the disease and give detailed information about causes, symptoms, treatments, and side effects. Try to be hopeful, but not unrealistic.
Kids this age avoid strong emotions and are able to compartmentalize their feelings and use distraction.
The child may want to help with a parent's care, but don't leave them in charge.
Help the child remain active in extracurricular activities.
Middle and high schoolers
Young teens 12 to 14 are ambivalent about dependence and independence. They may withdraw emotionally and may appear callous toward the sick parent's needs, especially if they interfere with time with friends.
Those 15 to 17 respond more similarly to adults but the duration of their grief is shorter. They can feel easily overwhelmed by the surviving parent's emotional dependence and grief.
For adolescents of any age, don't minimize the gravity of the situation. If the prognosis is not good, don't say, "She will be fine" or "Your mother will get through this. She's a fighter."
At diagnosis, you can say the chances of responding to current medicines are good or better than they were a few years ago, if that's true.
If the initial treatments don't work, you can say the doctors are trying experimental treatments that may or may not help. You can say you hope that the treatments will slow down or reduce the cancer. Acknowledge that you understand it's very difficult to live with not knowing what will happen.
Let them know when death is approaching so they have time to plan and make better decisions.
When death is near, say, "It is time to say goodbye" to Mom or Dad.
SOURCES: Articles by Grace Christ, of Columbia University, and colleagues in the Journal of the American Medical Association and A Cancer Journal for Clinicians
Jennifer Singer, an expert on grief and children at Penn Wissahickon Hospice, hosts a live chat 11 a.m. Monday.
Join the conversation - and read other stories by Stacey Burling about caregiving and dying, including last week's article about how parents talk with their kids - at www.philly.com/caregiver
Contact staff writer Stacey Burling at 215-854-4944 or email@example.com.