I suggest if you're not going to push back on your WW about taking the kids on her weekend you at least change the dynamic. Maybe you should instead pre-empt the request by asking to have them before she gets a chance. That way it is your wanting them instead of her using you. It's a big difference. And absolutely don't give her the impression you are doing her favors. You have things you want to do with the kids instead.
I have seen many her languish for many months by not heading sandi's advice when it comes to WW. I hope you are aware of that risk.
Me:49 W:45 M:19 T:22 EA confirmed and ended 8/2014 S:19,17 D:9,5