Thank you, JonoAubrey for your insight and welcome to TFP!
...but we have already decided to to go to St. Thomas. I realize that it will be very crowded and touristy, but being that it's the first time I've gone anywhere off of the continental US, I'm sure I will enjoy it anyway. Besides, I've no interest in shopping or hitting the usual tourist spots. What I want to do most is take the ferry to St. John and visit the national park there. Otherwise we will probably spend most of our time just wandering around taking photographs, drinking cocktails on the beach at our hotel and, eh, relaxing in our room.