I'm sorry you are having to deal with all of this sh**! I feel your pain at being "last". If I recall correctly, Yellowrose once told me that she at one time told her H to go back to the OW because she didn't want him anymore! Their sitch didn't have a kid in the mix, but he was being wishy-washy, and she finally got sick of it and put her foot down. Didn't answer his calls for several days after that. And then when she finally did answer his call, he asked her what she needed him to do to make things right, so she told him, and he did them.
I'm not saying you should do that, but I am saying that I think it's OK to stand up for yourself. I don't think you are obligated to allow your kids to go with him to the OW's house. I don't even think you would be out of bounds to insist that he pursue the legalities of visitation, and avoid contact with OW at all, if he really wants to work on your M.
And I think it's a great idea for you to go on the trip if you want to even if he stays home. I think that shows strength and independence (so long as it doesn't endanger your health).
In short, take care of you and let him figure himself and this crud out! You've shown that you can be supportive and accepting of the situation even in helping the OW when the child was sick! (Talk about above and beyond the call). Your H has seen it. Now he needs to wake up and appreciate it for the value it is!
You are amazing, and don't your forget it!!
((((((hugs))))))
TJ
Me45,H49 D24,S18 M26,T28 Bomb 3/19/08 Sep 6/23/08 EA/PA with Secretary 2007-8 3/2009 H moved in w/OW2 7/2009 Let him go w/Love. 8/2009 Legally Sep'd