AIBU to drop out due to friend cheating with married man

[KT84]

A while ago a friend confided in me she had kissed and been texting and ringing a man we both know, he is married and we both know the wife ( I don't know her well).
I was genuinely shocked by this and advised she stop seeing him before many lives were ruined as both my friend and the man have children.
This came to a head when on a night out I saw him and confronted him about what was going on, which he denied but I had seen some of the messages, which took the wind out of his sails.
He suddenly disappeared 6 months has passed and I have agreed to do a charity event with this friend amongst others as part of a team. There has been a group created where we can discuss the event and she has added this man to it (my friend is organising the event) he has also suddenly started to like all her social media content again.
I'm annoyed because I don't like him and want nothing to do with anything that may be going on. Should I drop out of the event to avoid the situation all together? A massive part of me wants to tell his wife.
AIBU?

If being involved makes you uncomfortable then drop out but it's nothing to do with you what other grown ups are doing. If they are making massive mistakes let them! It will all come out in the end.

I would drop her like a hot potato too.

There is shared blame, he is the one cheating, but she knows. More importantly than that, I could no longer trust her.

I'd quite happily be holier than thou tbh, I genuinely don't get the disingenuous attitude purveyed on here that it is totally cool to mess around with someone who is married. Of course the married person is the one who has broken vows, but that doesn't mean it isn't morally repugnant to behave as the OP's friend is/has. And in 'real life' I don't know of anyone who thinks otherwise.

but you dont even know what is going on, if anything?