Ahoy there, Mary Catharine! Welcome!
Disney Cruise Line has some pretty awesome destinations, and I think
Tortola is one of the best. It's a super family-friendly destination with pristine beaches and rich pirate history. And
St. Thomas, with its biking, snorkeling, and shopping - these are two beautiful Caribbean destinations.
In Tortola, Disney Cruise Line vessels typically dock in Road Town. The port there underwent a major renovation back in 2015, so not only can two larger vessels dock at the same time (previously, only smaller ships could dock), there's a proper terminal there now as well. If there are more than two ships in port on a given day, there may be a need to use a tender, but you may not have that information until you are actually sailing there.
When you get to St. Thomas, Disney usually tries to dock at Havensight Terminal, although it may be necessary due to congestion at the port or the size of the ship to dock at Crown Bay. Because this is a busier port stop for cruise ships, it might also become necessary to use a tender, which will take you to Charlotte Amalie, the capital city.
These docking decisions are many times made out of necessity, so it may depend on what time the ship arrives at the port, how many other ships are scheduled for the day, or even weather conditions. You may not know for sure where you'll be docked until you arrive.
I hope this information puts you in shipshape and ready to sail, Mary Catharine!
Anna