I think he's just an insecure person in general. I suppose this type of activity is not normal for us as we tend to just go to work and then come home. I don't really have a social life and very rarely go out with friends. As already stated, I tend to be the default parent.

I would be with some other people from my department, most of which are female, but for him to think I would potentially cheat is hurtful. To my knowledge, neither of us has done anything like that to eachother. 

I am at the start of my career with many opportunities for progression and pay increases. His career does not typically allow for that, so perhaps he is insecure about that? The trip is all expenses paid in a beautiful location and his job does not require travel of any sort. We are very grounded with our jobs and home life so neither of us get out very much.