My XW did/does the exact same thing with me. She always wants to go out to dinner or do activities all together with the kids. I went along with it quite a few times. each time we would have a great time.
It would leave feeling so hurt. I just could not understand why if we are getting along so great don't we continue doing it to build on. I would feel so down for days. My 8 year old daughter would also be upset.
I would suggest that you don't go to lunch with your X. Everyone is right when they say that you XW just wants to show herself and the world that everything is ok. I think they do this to feel better about themselves.
Me/W: 46/36 D7.6/S6 T/M: 7.5/6.5 Bomb 12/05/07 D final: 03/03/09