We've been to St Thomas a few times with Disney, I've had days with and without excursions. There's plenty to do in the area. Magens Bay can get very crowded, especially if there are multiple ships in port that day. You can take a taxi to Coral World, we had a great time there. Coki Beach is literally next door to Coral world if you wanted some beach time as well. Havensight mall shopping is very close, but not very exciting (to us at least, I guess the port shopping malls can get stale after a while). There's a butterfly garden super close (easy walk) to the port. I will say... the BEST day of my life was on a port adventure in St Thomas, taking a pirate ship cruise to Buck Island and swimming with sea turtles in Turtle Cove, along with a beach break at Honeymoon Beach & lunch on the beach. It was magical! St Thomas is an amazing destination, I hope you enjoy it!