MIL comes over and watches kids on his custody time. So she now has pretty much limitless access to the grandchildren. No dil telling her "we have plans on Saturday, but we can see you Sunday." Much better arrangement for her. No more calling me screaming I was keeping the kids from her despite the fact that she saw them two days earlier. Very little incentive for her to do anything but be a cheerleader for the divorce, if you get my drift.
My MIL is also a cheerleader for the D (my parents and FIL are not) and that's frustrating and makes me angry. My entire family (parents included) went to her house for Christmas dinner just last year. 2 months later was BD and she has not reached out to me once since.
I don't mean to make light of your situation, because I certainly understand through my own how difficult it is, but there is a slight silver lining in that now you don't need to worry about MIL's demands on you and your kids time AT ALL during your 50% with the kids (and 50% without them). Obviously you'd rather not be where you are, but many that can bring some slight relief to you.
Me:39 Ex-W:37 M:7 T: 9 S:6 D:3 BD/IHS/Confirm EA/PA: Feb '20 OM1 affair ends: May '20 W/OM2 & moves out: June-July '20 W files for D: Jul20 OM2 confirmed: 9/2020 Divorced: May '21