I agree about the Sonesta. My husband and I stayed there for a week a couple of years ago and really enjoyed their private island - it was very relaxing. To the right of where the boat docks is the "adult" beach - some topless people, but much quieter than the other side. Although, the restaurant is on the other side (not very far, however.
If you like snorkeling, I highly recommend De Palm Island off Aruba. We took a bus, and I do NOT recommend this mode of transportation. The driver dropped us off in the middle of nowhere and pointed through this residential area. We walked through a rather scary neighborhood with mean-looking, loose dogs roaming around. Fortunately, we made it to the dock to get the boat to De Palm, but I recommend taking a taxi or ship excursion. Anyway, we saw the most colorful fish we've ever seen in the Caribbean (we've snorkeled in Grand Cayman, Cozumel, St. John). The only place we've snorkeled that was better was Haunama Bay on Oahu.