FYI for your visitors: we've flown into/out of Antigua, St Maarten, Guadaloupe, Martinique, and Grenada with no hassles, usually a short cab ride to a nearby bay or marina to meet friends on their boat. Most of the islands have some sort of air service. The local hop flights can be disproportionately expensive, but it's nice not to have to 'circle back' when you only have a couple of weeks.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)