I haven't read your own sitch, but I am generally in favor of exposure to ADULT children, OM/OW's spouse, the wayward wife's parents and siblings, and your own parents and siblings. I also exposed my wife's affair to their employer, since their affair was happening at their workplace.
Most of your kids are too young, in my opinion, although I wouldn't LIE to them if you're ever asked a direct question. Your oldest child is a tougher call. I ultimately decided to tell my son, then 14, when he asked me why his mother and I were fighting all the time, and I suspected he had seen and heard things and must have been horribly sad and confused. So I told him in an age-appropriate way, "Mom has a boyfriend, and married people shouldn't have boyfriends and girlfriends. It's not right, God doesn't like it, and it makes me very angry. I've asked her to stop, and she won't, and that's what we keep fighting about. I'm sorry I had to tell you, but I will never lie to you, son. This is NOT your fault! If you want to talk about it, we can, or we don't have to. But I wanted you to know the truth, and I will never, EVER lie to you. OK?"
It was the hardest, saddest thing I had to do throughout my whole ordeal.
I also exposed to our two adult daughters, then 18 and 20. All three of those children already knew, btw -- something to consider.
Exposure can be a very effective tool in breaking up affairs and restoring marriages, and many counselors and books advocate it. Each person has to weigh all of the information, however, and do what's best for them. In my own situation, my wife told me afterward that the pressure from her mother and one of our daughters, in particular, played a great role in her ultimately deciding to end her affair. And while she was livid with me at the time, she also told me she loved me and understood that I was only fighting for our marriage.
