Talked into it?!? shit, wouldn't have to ask me twice. Those islands are great!! Have a great time!
St. John is probably the best of the U.S.V.I. by the sound of things. I've only been to the B.V.I's and I'd imagine that St. John would be the closest match to them because it's not as built up. Besides sailing and snorkling which are both great, especially the sailing, scuba's great, a lot better than snorkling in my opinion. It looks like theres a great national park there to check out. And if all that's not enough, I recommend Rum. It's cheaper than mix there and reallllly good stuff.
check out the link:
http://www.here.vi/USVI/St__John/st__john.html