I don't have much of an answer for you, but I have the same issue I am taking a thanksgiving family trip with W and kids. My plan is to be friendly have fun with the kids and try not to think about R stuff. As far as the other stuff like not getting dressed in front of you or not touching you who knows what to think. My W will freely get naked, shower and everything right in front of me as will I, but she will not lay in the bed with me or touch me.
Again for you trip my advice would be to act as if, be upbeat, be the person your W will miss not having around.
Me - 34 W - 33 S - 5 D - 4 M - 14 years Bomb 1 Dec 06 Bomb 2 Aug 07 Separated - Aug 07 WAW Renting own place - Dec 07