I would also recommend -

The Jacques Cousteau Marine Park at Pigeon Island, Guadeloupe - really fantastic snorkelling and diving.

St Vincent - often overlooked but hard to beat if you like stunning scenery, hiking, waterfalls, botanical gardens and an active volcano that you can hike. Cumberland Bay is rather a good spot these days - a couple of really fantastic places to eat/drink, very friendly folks, no hassle from boat boys, and a great place from which to start a hike.

Further south, Blue Lagoon is also quite a decent spot with some good restaurants and facilities