This is my metier, StreetFighter, I was that woman, the one that you are trying so hard to be in a room with. Unlike yours, I feel only shame and disgust for my impact in someone else's marriage, so I will post a bit about how I think OW will be feeling and perhaps that will give you some insight and best strategy for dealing with her presence.
OW possibly feels like this:
- sadness at the ending of the affair and perhaps a bit bruised
- wanting some sort of validation that the affair meant something to your husband
- bereft at the now missing attention/affection
- anger at you for 'winning' and that your husband has 'chosen' you
- wanting to wrongfoot you if she can (because she sat next to you, I would never have done that!)
- wanting to parade in front of both you and your husband as the prize specimen that she feel she is.
.
It's an uncomfortable notion that a wife can never give the same 'dazzle' as an OW can but conversely - and this is the important bit - an OW cannot step into a wife's place and that place is assured - and, if you want it, for life.
In reality, OW doesn't know that you'll be there so you will automatically wrongfoot her Your husband isn't attending so she will not have the frisson at seeing him. I was a bit on the fence about whether he should attend with you or not and, if you think it would make your time there more stressful then he should not. He would need to 'play a role' and from what you've posted, he isn't up to it.
Far better that he picks you up. That 'picking up' in itself is an indication of closeness and togetherness that OW will not have with your husband... it will hurt her. If you want to rub salt, arrange to leave just in front of her so she sees this BUT it's important that you make no drama of it, if you do she will see it for a charade and it will wrongly but adroitly validate her own behaviour to her.
I would urge you very strongly NOT to approach her nor make any acknowledgement of her. She will be sensitised and possibly alarmed at your presence and, as her affair with your husband is now over, there may be some ill-formed desire on her part to prolong the involvement as that would give her validation that 'the Affair' meant something. Don't do it.
If she crosses your path and tries to engage just say "Excuse me" and walk around her/past her. Say nothing else.
If she sits next to you at any point then get up when convenient and go to sit somewhere else.
If she does the unthinkable and actually corners you in conversation then look her in the eye and tell her that "If you approach me or my children at any point in future, I WILL let your partner know what sort of woman he is with. I trust we understand each other.". And walk away.
At all costs, appear as yourself. You can be as groomed and lovely as you like but one false step noticed will invalidate all of that. So be yourself... you know the other people in the room presumably so greet them, smile and engage in small talk - and enjoy your child's performance because that is what you're there for.
You can do this, StreetFighter. No sweat...