Being Me, the kids do know that Mom and Dad are not getting along. After our huge blowout last summer, which the kids unfortunately witnessed, I sat down and had a talk with them in the evening (W just left, when kids asked if we were getting divorced she said she didn't know and left!). I explained the situation, leaving out OW. I told them that Mom and Dad hadn't been getting along for a long time. I said that Mom didn't love Dad in the way that Dad still loved Mom, this happens sometimes when couples have been married a long time. I told them that Dad was going to stay and work hard to make things better but couldn't promise Mom would love me again. I said Mom can't help the way she feels and I can't make her feel differently, if I could I would! Kids were worried I might walk out like a few of their friends Dad's did, I promised them I would NEVER do that. I also told them I couldn't promise mom and dad would always be together but that they would always be the most important people in our lives. I think I handled it beautifully and unfortunately single handedly. So, yes, they know the score. How much they know about Mom's "friend" I'm not certain. Thanks for your insight and experience, it helps a lot!
