Hi Brittany,
Thank you for visiting the Disney Parks Moms Panel with your question!
I think you could have a fun day at either Disney's Hollywood Studios or Disney's Animal Kingdom. It depends on the interests of your traveling party which one will be a better fit. I suggest that you take a look at the
Walt Disney World planning video to see which theme park appeals to you more. You can also check out the webpage for
Walt Disney World with preschoolers for ideas specific to planning with little ones.
Disney's Hollywood Studios is a great theme park to visit if your little one loves characters from Disney Junior. There are opportunities to meet some of these characters, as well as the great and energetic show Disney Junior - Live on Stage! There are also high-energy and fun character dining experiences available at Hollywood & Vine, some with Disney Junior characters and some with Minnie Mouse and her friends.
At Disney's Animal Kingdom, you will be able to see many exotic animals. There are great walking trails to explore and view animals. At your son's age, my daughter also loved a ride on the Wildlife Express Train out the Rafiki's Planet Watch where she liked to brush goats at Affection Section. You can also explore the amazing new Pandora - The World of Avatar, where the landscape is amazing and your whole family could ride the tranquil Na'vi River Journey.
If I was making this decision, I think I would choose Disney's Animal Kingdom, because I think of it as a theme park with many lush and calm areas that you can explore at your own rate, which will likely be a good match for pregnancy. However, I also think you could also have a wonderful day at Disney's Hollywood Studios!
I hope that these thoughts are helpful for you, Brittany!