Treese, I am so sorry that your daughter was cut from the team. Life can be so hard at 16yrs. I remember all those highs and lows with nothing inbetween.
I find it so hard to believe that any man would do that but I do believe you. Was the mother a one night stand do you think because she seems to have kept her "secret" for the past 8 years? I know it is really hard to think any good of OW, but when you consider how much he lies maybe it is possible she just didn't know. I guess 8 is about the age whenthey would start asking questions about their Dad. Did your H know of his existance all the time.
Anyway if you are sure he could do this accidental meeting you must let him know how you feel. You haven't much time to arrange a meeting with him so not much time to ponder.
As he is now with another woman he can't have felt much for the other.Does that make a difference I don't know.I think the blame lies more with your H than the ow. Does make you wonder how many othe women there might have been.
So have you considered what you will say? Take care.