What do you mean what can you do?

You tell her NO Ken... or you go and when you get there you tell her that you are BOTH leaving RIGHT NOW with these children or you are goin gto tell EVERYONE In the ROOM she's having an affair with that man right in public

Tell her if she wants to be humiliated in public you are more than happy to do it... Don't WARN HER... tell her no you don't want any of your family there..

If she insists you go along to and suddenly make a scene exposing her affair to everyone in the room.. do it and she will be ashamed of herself and it will resonate for weeks... do it Ken