Howdy Bernoulli Fan,

I don't know anything about specifics on renting a floatplane down there. Does sound like fun for a honeymoon- You mean renting one for you to be PIC, right?
Got a few buddies who have worked on floats out of Key West, and at Jack Brown's, but all I know of floatwise in the Caribbean is Seaborne, with their Twin Otters.
Maybe somebody else viewing knows more, but in case not-
here's a link to the Seaplane Pilot's Association website, perhaps they have info?
Or PM me and I'll try to see if the above mentioned friends know of anything if SPA has no info on it.
Congrats on the getting married deal!

Contacting SPA - The Seaplane Pilots Association