wh, Shouldn't your xh be communicating w/you and discussing these camps that he's signing the kids up for? Both of you should be splitting the costs for those camps down the middle. I know that you are willing to pay your share of expenses...but something isn't right about this scenario.
Maybe he thinks that if he pays for the camps, then you should be paying for the sitter, which could eat up a chunk of change next year.
I think you may want to document this discussion and keep it handy because I think you are going to be put in the hot seat over finances for the kids.
I still don't trust him one iota.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.