The children and their mother were at the North Philadelphia corner selling fruit to raise money for a neighborhood playground.
The 45-year-old woman whose SUV was stolen during the carjacking was also injured in the crash, as was another woman selling fruit, Thelma Brown, 69.
Alexander said a funeral for the children had been set for 11 a.m. Monday, and she thanked the North Philadelphia Seventh-day Adventist Church, at 16th and Oxford Streets. "Pray for our family," she said, mentioning the children's two surviving sisters.
Moore thanked former 76ers star Charles Barkley for offering to pay for the funeral.
Jonathan Rosa, 19, and Cornelius Crawford, 24, were charged with second-degree murder, kidnapping, sexual assault, and related offenses. They were arraigned and were being held without bail Tuesday.
Police said Rosa and Crawford approached the 45-year-old woman, a real estate agent, Friday morning near Sixth and Cumberland Streets, forced their way into her Toyota 4Runner by implying they had a weapon, and assaulted her sexually.
The men drove the 4Runner north at high speeds and lost control at Germantown and Allegheny, police said. The SUV jumped the curb and careered into the fruit stand.
Police launched a manhunt to find the two, receiving help from witnesses who flooded the department with tips, looking to help. Neighbors and local businesses sent in video footage of the area, and police said several witnesses were able to identify Rosa and Crawford once they were taken into custody.
Rosa turned himself in Sunday night. Crawford was found hiding in a shed behind a building on North Sixth Street the same night and taken into custody. Both gave statements to homicide detectives, police said.
The crowd assembled for Tuesday's rally spilled into the streets, which were shut down by police.
Deputy Mayor Everett Gillison, Mayor Nutter's chief of staff, thanked the community for providing crucial leads for homicide investigators.
"You helped solve this case," Gillison said. "Thank you for what you did. You stood up and did the right thing."
Anthony Murphy, executive director of Town Watch Integrated Services, said residents who had information did not abide by the "don't snitch" street code.
"This is our community, and we are responsible for what takes place," he said.
He added, "Working with the Police Department makes a difference. You proved that."
Bilal Qayyum, president of the Father's Day Rally Committee, and State Rep. W. Curtis Thomas (D., Phila.) said donations for the family can be sent to Education Works, 3149 Germantown Ave., Philadelphia 19133.
Education Works, a nonprofit, is across the street from where the crash occurred, and employees ran to the aid of the victims.
Inquirer staff writers Mike Newall and Aubrey Whelan contributed to this article.