I'm pretty much with the others. If you don't love the quilt, don't finish it. I don't think I would make any quilts for the three of them either. The two girls seem to have issues with following through with what they start and your son is too picky. I would be thrilled with a quilt someone made for me, butterflies or not. It's clear he has no idea the work involved in trying to remove a piece from a quilt without damaging the fabric around it, let alone properly sewing a new piece in. To me that's a disaster waiting to happen.
Spend your time making what you enjoy because you enjoy it, not because someone wants you to. Finish the quilt if you like, but finish it the way you want it. If you like it someone else will too. If you find yourself forcing yourself to work on it you might want to ask yourself why and maybe just move on to a project you do enjoy.
My 2 cents,
Rodney