I think it is time for you to inform your kids about the situation of your M. They will find out soon or later.
Our kids discovered their mum's A by reading the sms sent by the om. So I don't need to add anything. Therefore they are all supporting me. My D is feeling sorry for her mum. My W tried to tell her that she was unhappy etc etc to justify her A. But my S can't understand why his mum did what she did.
It is normal when you love your S, you try to hope that your S will wake up one day and come back. I did the same. I tried to accept any excuses my W has given to me about her A. I wanted to believe that she has let go the om. But the reality is different. Finally she made her decision to move out and lives with the om. It was hard initially for me. But it also gives me a clear direction to go. Until today, I still can't talk to my W alone. I am still hurting. But living alone without seeing her is fine for me. Therefore I can understand your feeling about how difficult to be with your H on the swim meet. Both of us still have to learn to detach from our S. I need it as I may have to see my W alone soon to settle our property.
