DH & I went to Providenciales in the Turks & Caicos for our 10th, 15th and hope to go back in a couple years for our 20th. We love it there. We first chose it because of the time and ease to fly there and it would be easy to get home if something came up. We leave MYR around 7am, one short layover in CLT and are on the island at lunch time! Flight home leaves at 3 so we get one more long morning walk on the beach and nice lunch before leaving and are home by 11pm. When you only have 5 days its great not to waste a whole day on each end traveling. The water is gorgeous, the sand is soft & white and the island is very safe. We rent a car and explore everywhere. The snorkeling is good too and I can give you the companies we used if you are interested. We stayed at the Royal West Indies both times, visited the Sands, and Ocean Club and Ocean Club West. Would stay at any of those in a heartbeat. They are all on Grace Bay Beach. Like most on the island they are moderately priced, condo style resorts. There are no skyscraper buildings, most are 3-6 floors with a very few being maybe 10-15 floors but those are the new high priced places. There is a grocery store near the resorts for wine, beer and sandwich stuff. There is not much nightlife so if you are looking for action this may not be for you. T&C is like the Bahamas in landscape, flat & dry. The resorts are beautifully landscaped.
I would consider staying on St Thomas just because of the deals on hotels there but I would use it as a jumping off spot to day trip by ferry to the surrounding islands like St John (would much rather stay there) and Tortola (would love, love, love to stay there). Also, from looking at friends pictures I would go to Playa Del Carmen, Mexico or Punta Cana, Dominican Republic. The resorts they stayed at were beautiful. They were affordable all inclusives and the air fare was very reasonable. But they did have to stay in the resort areas and not venture out due to safety.
Hope that helps and Congrats on your 25!