agree about telling her "maybe but can't say for sure now".
I think going would do two things and risk one thing. The risk would be that you feel crushed if she goes with OW, and she might not, given that her family loves you and wants you there.
But the 2 things you could achieve are, SHOWING her the new improved you, w/an upbeat attitude and GAL under your belt and the traits she fell in love with, all aglow in the New improve you....
and second, you'll solidify the relationships you have made with people who mean a lot to you. You can stay in their lives. (Plus they'll probably say something to your w about leaving you and that might not hurt...)
But You don't have to lose everyone in the family even if things don't improve with your w.
ALSO, don't assume that b/c a paper is signed off on, and a divorce is final, that remarriage is impossible. I've seen 2 family members remarry their former spouses, a few years later.
I see my former SIL about every year, (we live 3000 miles apart) and we fb each other often, call, and we vacation together every other year. We're pretty close.
So yes it's possible to do so. If you can handle the risk, I'd plan on going. But be careful with your heart.
And as Snodderly said, you don't have to commit NOW do you?
M: 57 H: 60 M: 35 yrs S30,D28,D19 H off to Alaska 2006 Recon 7/07- 8/08 *2016* X = "ALASKA 2.0" GROUND HOG DAY I File D 10/16 OW DIV 2/26/2018 X marries OW 5/2016