Please, don't do or say anything that might jeopradise (sp?) your relationship with your children. That relationship is waaaay more valuable than any quilt...or anything at all.
I do appreciate your time and workmanship in this quilt and I'm so sorry that it has been abused. Be happy that they use it and I'm sure they love it. Go with the flow and don't give them another heirloom quality quilt. They probably will like the simple ones just as much.