Hey girl! My family has the same kind of relationship that you and your family does!
We are debating vacations next year also. I want to go on a cruise.........but don't know if they allow more than 2 in a cabin! LOL! But surley they do being that people do have kids and all.
I hope you find a place that is great!
I would say that you should go wherever you guys want to go. If people don't like seeing the three of you together they can always turn their heads. That's how I feel about it.
I'm going to be proud to have our GF on both of our arms. And I refuse to let snide looks take that away from any of the 3 of us.