Irene, welcome back and congratulations on the news of your newest little family member who will be arriving later this year!
The ports in the Eastern Caribbean are all stunning and offer such unique experiences. Since you'll have two little ones with you, and being pregnant, yourself, you'll want to enjoy one of Disney's Family Port Adventures, which tend to be more mild, but still immerse you in the local culture.
In St. Thomas and St. John, I'd recommend the
Coral World an Butterfly Farm tour. Not only do you get to visit Coral World and see the amazing undersea observatory, but you'll have some extra time there to hit the beach. Then meet back to join your tour as it heads off to the Butterfly Farm. You'll have a blast as your girls hope to have butterfly friends land on them, and even get to watch a fun parrot show! This place makes for some great photo opportunities!
If that short beach time in St. Thomas wasn't enough for your family, you might also consider the
Isla Verde Beach Escape in San Juan, Puerto Rico. You'll have about three hours to simply relax and play at this gorgeous beach, knowing that since Disney has taken care of all the details, you won't have a care in the world! A great authentic Puerto Rican lunch is included in this adventure.
Of course, there are ways to visit a beach in both spots on your own by taking a taxi, but with two little ones and another on the way, if I were you, I'd go with one of Disney's preplanned adventures, as you know that they will very easily get you there and back and you only need to show up, ready to relax and enjoy.
Have a wonderful trip, Irene!