Im just getting up to speed on your sitch...holy geez...your sons play soccer together?!?! Good lord! I'm so, so sorry.
Sadly, I have a friend who's H did the exact same thing. They have reconciled and her H can no longer attend the sons games. Sandie is right it's an addiction and her H is not allowed to be anywhere near where this mom is at. Her son knows all about it. Just sad.
I really don't have any suggestions. Honestly, if my OW showed up somewhere knowing I would be there...wow, balls. I wouldn't say or do anything. I haven't contacted her ever. I've never met her, but know many who know her and could make her life very, very miserable. Not my bag. But, I'm surprised your wife is attending the game. Sounds like OM's wife wants her to stay away. Am I reading that right? I need to read back further. It's a PA and are they trying to end it or not?
Mainly, there is nothing you can do. If OM's wife makes a scene, so be it. It is called consequences. You shouldn't stand in the way of your wife feeling them, and frankly, she should have to feel it. These are reprocussions of her actions.
M: 9 yrs T: 13 yrs H:34 Me:35, S4, D2, S 7 months Dday 11/12-PA & multiple PAs Dbing 12/12 S 1/13 7/13 H moved back in basement. 8/13 #3 born 10/13 still cheating 10/13 He moves across country, I file for D