St Vincent and the Grenadines is within 30 minutes by internal flight SVG Air (not OW obviously but I think you will struggle).
We stayed on an island called Canouan in SVATG and it has a superb resort called Raffles. From there you are within about 30 minutes by boat of the Tobago Cays where they filmed Pirates of the Caribbean. This is some of the best reef snorkling/diving in the world.
Alternatively fly to Union Island and get a boat across to Palm Island and stay the night there - it is a tiny island with just the hotel and you can walk round it in 40 minutes.
www.wheretostay.com is good for hotels in the Caribbean.