Vow Renewal OFF Cruise Ship

My husband and I would like to renew our wedding vows while on a cruise. We don`t want anything fancy, as it will just be the four of us (our two daughters included) plus anyone we meet on the ship and may invite. We have the following ports to work with....
Charleston, SC, St. Thomas (Easter Sunday); San Juan, PR.

I`ve been scouring the web looking for ideas to no avail.
Suggestions will be warmly received!
P.S. We are not interested in what the ship has to offer, it`s done in large groups and not very personal. We`d rather go to the chapel when it`s empty and just do it ourselves.... But we`re open to suggestions.
We have three 1/2 weeks before we leave.... HELP