Kevin, I specifically explained to my kids what an affair is and why it's wrong.
I said: 1. An affair is when a husband or wife has a "boyfriend" - something that no one should ever do. I called it "cheating" - kids understand what cheating is. 2. The reason it's wrong is because Mommy made a promise to God and me that she would be with no one else while we were married.
I wouldn't bring it up unless the kids ask about it. I don't shove it down my kids throats - I even tell them that I don't think Mommy's a bad person, just that this is something that is wrong.
W has never argued with me - or said anything different. One time she told them that we WOULD be divorced if she had the money, and that's the only reason. So, I told the kids that we could be divorced, and I offered to pay for it, so Mommy has no reason.
I never say a single negative thing ever about W - but I don't hesitate on this.