Chicki - I would BLOW UP if my H took my kids on an overnight w/OW. Do whatever you want to me but leave the kids out of it! If for no other reason than your kids, you and your H need to stop attacking! Set some clear boundaries around interaction with your girls. I know it's easier said than done but those girls deserve a more stable home life. Set some boundaries and see how you feel next week...
I was so angry that OW helped H pick out a gift for my child. I can only imagine how YOU feel right now..