Wow, my fh and I have been going back and forth with this issue too. We were going to do the legal ceremony December 31, which is our anniversary, but we had trouble coordinating our parents since they don't live in the same area as us. We have ultimately decided to just go ahead and get married a few weeks before we leave. If the parents make it, then great but if not, they will be at the Punta Cana ceremony.
I view the Punta Cana ceremony as the "real" wedding in my opinion so I was wondering about that ring exchange thing too! I kind of figured that we would not exchange rings until Punta Cana and that's that. In regards to the legal ceremony, I know me, and I know him, so I know we will have to wear something nice to at least make everything look decent. I'm sure we'll take a few pictures that day and also just go to dinner and that's that. I think it's going to depend on our parents to be honest. We aren't trying to make too much of a big deal out of the legal ceremony and I wanted to keep it secret, but with our family that just isn't going to happen so I gave up on that idea.