Regardless of how you W is acting you need to also understand that your son will also remember how you acted. So I guess my question would be: How do you want you son to act if this happens to him down the road? Do you want him to think that it is ok to give up without a fight or do you think he will believe you left to protect him?
I'm not sure what his age is, but you need to consider what will make a bigger impression on him. I wouldn't take W's action into account on this because you have no control over that. Who says that if you caved in and let her have her way that she is going to be any happier? You have to realize that her view of reality is a little distorted right now. The newness always wears off and all the problems that weren't dealt with before always come back. Took me being D from 1st wife, having problems with 2nd W to see that.
"Our life is what our thoughts make it."
Marcus Aurelius
