Do you think it might help to approach C by asking the W if she thinks your kids will benefit from living in a disfunctional home? Did her growing up in one benefit her?
I'm thinking of you saying something to the effect that you don't know which of your M ideals is the "right" one but you both owe it to the kids to find out. It might make her stop to think. I'm guessing that she already knows her idea won't hold up in C, but at least you'll be approaching it for the kids rather than against her.
