Not sure this is the best place to post this as it seems more appropriate in the divorce forum but it also seems preachy or judgmental to post there... So here it is.
My husband was the BS in his first marriage. After ten years of marriage, and with a two year old child, his wife had an affair with his best friend who was also their minister. She left my husband for her AP and is married to the guy and has been for 21 years now.
My husband always took the high road. He never fussed about attending parent teacher conferences with his ex and her husband. He always bought gifts for the child to give to his ex at birthdays, holidays, etc. until she was able to do so herself. We attended every conference, play, recital, etc., that child ever had, along with his ex and her husband. He never argued about visitation or child support (neither did she, luckily). The child had never had a clue that mom cheated or that the beloved step-dad was an AP. She never had to have any discomfort with having all four of her parents in the same room.
That their child is now 26 and just received a PhD. There were several dinners and breakfasts plus the ceremony that we spent with his ex and her husband. The adult child, as always, did not have to worry about who to invite, who would get along, whether anyone's feeling would be hurt. It's simply never been on her radar that her dad might not want to hang out with her mom and mom's husband. And, to be sure, they have not always made this easy for him.
I've always admired this about my husband. He has handled his situation with grace and enormous love and respect for his child. I'm so proud of him, once again, for this.
And, quite frankly, I do not think if he ever cheated on me again, I would be able to stop myself from telling the kids, even knowing how wonderful it is to keep the kids out of it. In that sense, he is a better person than I. It's this sort of thing that reminds me why I love him, on the days when it's hard to feel it.