I honestly don't get about the H, ex-W, and affair partner hanging out, with the H and ex-W going to lunch at times. I think it's absurd and degrading for the LBS. I am way more of the 'you're cut from my life' kinda guy, with the only exception being stuff related to kids.
I know that never say never, but I cannot imagine doing that with ex-W. And I don't say that out of spite. I just feel that if i did that i would not be honoring myself and my own self-respect. But, that's me.
Never thought this would happen to me ever. I wouldn't even meet OW until after they were married and that was a few years.
However, now my daughter, my ex and his now wife, AP, stepmother to my daughter will have an occasional meal together, sit together at kids events, and he had his sister invite me and our daughter to his sisters superbowl party (I was close with his sister, she didn't mind) and we all hung out.
Now, would I do this if we didn't share a young child? No way. But my daughter was very uncomfortable when we were separate at the same places and I had to show positive communication for her comfort. Now she is comfortable around all of us. I wanted to minimize the effects of having 2 homes, and I believe I've done an excellent job. Sure, I took a bullet for my kid, but I would throw myself in front of a train for her.
This isn't for everyone. But I do suggest it where there is a young kid, who has positive feelings towards all involved. OWW has been in my daughter's life since she was baby. That's her stepmother (I also like her better than my ex, believe or not).