Did 12 days in St Lucia - 5 sailing and a week in a villa - with a carry on bag and a shoulder pack. Had snorkeling equipment with the large ScubaPro flippers and scuba booties. We'll be there 9 days this reach and I would never think of taking more than I did for that trip. Underwear is highly underworn in the tropics. I only take a few pair and always seem to bring back some I never wore. 3 suits - wearing, dry and drying. coupla shorts. coupla t-shirts. 1 or 2 long sleeve UV shirts. Wear a nice going out outfit on the plane. Wear the Keens, pack the Birks. Essentials only in the 3 oz carry ons, buy sunscreen, etc there.
You guys are going to be highly mobile, I know folks who would say you're overdoing it with a rolling carry on for your itinerary. They'd be running with a knap-pack and a Euro-bag with all your moves. Essentials are much less than you might think if your constantly traveling. I'm clearly a proponent of less is best!![]()