I did just that myself. We got married at the courthouse last week. So that way all our papers are here in Canada, when we need a copy we can get it in a couple of days instead of weeks from the caribbean. And I wore my wedding dress at the courthouse. I even saw some couples with flower girls, stretched limo and the whole shabang. Afterwards we had a coktail hour at our house. We kept it secret and simple (we were a total of 20 people).
Basically you'll have a vow renewal ceremony in the caribbean ( no worry no one will even suspect it's not a "real"wedding)
Hope this helps