St. Thomas has two places I go everytime, creature of habit I guess. The Skyride to Paradise Point which is within walking distance when you get off the ship. When you get to the top (you ride a suspended cable car) you can look down and see all the ships and small islands. The are some shops up there and a patio bar & grill, you have to order the famous Bushwacker drink. Frozen Baileys and cream really good.
My other place is Magen's Bay. Not much going on there just a very peaceful quite cove and the water is pretty calm.
St. Maarten you can ride the water taxi, usually $6 for round trip as many times as you want. Shops are lined up and down the streets, patio bar, beach front and one musn't forget the best place THE BELGIUM CHOCOLATE FACTORY! That is an absolute must, the chocolate is to die for.
Whatever you do you will enjoy.
Happy cruising