Update:
Wedding is over (little changed after, save some legal paperwork getting done, likely), and it was rough. In the end, the one kid that had any desire to be at the thing (to support dad, not the marriage), ended up not going to the actual ceremony, as few to no precautions for the virus were present in the rehearsal. Xwh was said to be saddened by that, but at least indicated to the kid an understanding - not without first trying to manipulate/coerce the child to go anyway. Mow was worse, both trying to manipulate the child into still going and then basically accusing the child of lying, indicating mow thought I had gotten the child to decide not to go. Nope, I let the kid make the decision and then just helped the kid keep to it. (I am sure mow took to social media to blast me for making it be that one kid backed out like that....mow is like that.)
Child learned something, though. Child had thought mow was "ok" though was simply tolerating her. Child now knows this is how mow behaves, as I let the kid knows this is what mow does to people - she lies and exaggerates and denigrates to manipulate people when they don't follow/agree with her choices; I warned the child mow moves on to telling others these lies and exaggerations in order to gain the pity for her seeming the victim and her target the villain, when the opposite is much more true.
As for me, I chose to go to the hotel for a few hours the rehearsal night and treat myself to a steak dinner as well. I did not really sleep the night between, crying off and on, not just for me, but for my kid(s), due to all the circumstances, including the difficult choice on the one kid. (Other two are not ones to stand up for selves against xwh, fearing the repercussions.) My crying for me had a lot to do with the finality of xwh completing his discard of me; as xwh actually told child, "it was a closing of a chapter in his life" (and mine) - for him, he got the beginning of another chapter WITH another, but I am alone, and may always be (somewhat choice at this point, but brought on by the A/D, as my ability to trust, with any real intimacy, is gone). I had planned to go back to the hotel the next day, but child's decision changed that, and we spent the day together instead.
As is the thing to do here, mow gave the kids gifts for participating in the wedding. As part of it, there was an item that celebrated the new legal relationship between mow and the kids, as though it was a real tender, loving one. This is both amusing and irritating. It is amusing mow seems to think my kids have or even want that kind of relationship in reality with her that would make this gift endearing to them; it is irritating she seems to think she has successfully totally replaced me now, as has seemed to be her goal from the start of when she decided it was time to convince xwh to leave me. (I don't want to be too specific on what the item is or how it celebrated the relationship; you will have to trust me that there is a lot that was done during the D and prior as well as in this gift that shows this to be true - and others who do know these details agree with me on it.)
At least the wedding is over, and I can go back to ignoring that mow exists and just being annoyed xwh does. (But,I do still have to wait out the self-quarantine time with my kids, praying neither they nor I get sick, thanks to the lack of precautions taken and enforced by xwh/mow. Sigh.)