If you are trying to detach and trying to stop parenting, then why are you still judging W's actions and trying to shape them?
W asked if the babysitter could bring the kids to your house. A simple, "no, that doesn't work for me" response is all that is required, to her and INTERNALLY.
Instead, you judge her parenting skills, consider how best to get her to grow up and deal with the babysitter, etc, etc, etc.
Guess what: this is no longer about stuff that happened between you many months/years ago in your M. It is only about the present.
BTW, why are you paying for babysitters on W's time? Is this something over and above child support? You don't get to choose to do this and then resent that it isn't being implemented how you want. Don't give gifts that you want to control. They aren't nice.