DEAR ABBY: I had to respond to the letter from "Discordant Family." I agree with you that the children should not be forced to play piano. However, let me offer an alternative. Many young pianists quit because practicing is such a solitary chore. I'd recommend finding the kids a community music program they would enjoy.
Perhaps their friends are involved with a chamber or duet group, or a music camp. Set the completion of the group project as a goal and allow them to move on (if they still want to) once they've reached that goal rather than quit on the spot.