There's nothing about "detaching" that says you can't discuss the family's finances or the childrens' logistics with your spouse. Just do it in a friendly and businesslike manner.
I think her plan for the party is a bunch o' b.s., for what it's worth. I think she just doesn't want you going to that party because of what you might tell people. Still, that being said, if she is willing to trade that off so you can take your son to one game, and she can take him to another, I think that would be a good thing, since she never goes to ANYTHING of theirs.
