Hi Gabriel,
Thank you so much for visiting the Disney Parks Moms Panel with your question. I have always been of the opinion that there is plenty to do for
young children all over Walt Disney World. I do tend to recommend that everyone try Magic Kingdom as it has many attractions for little ones and is where the magic all began in Florida. Since you have already gone to Magic Kingdom and Disney's Animal Kingdom, you know that there are many attractions there appropriate for little ones. If you and your son loved those theme parks, then go ahead and revisit them! There is always something new to do.
If you are looking to try a new theme park, Disney's Hollywood Studios will be a great fit if your son enjoys the Disney Junior characters. From meeting these characters, to seeing them on stage in Disney Junior - Live on Stage!, to dining and dancing with them at Hollywood & Vine restaurant, the Disney Junior characters are all over Disney's Hollywood Studios.
Since she was little, my daughter has identified Epcot as her favorite theme park at Walt Disney World. She was always up for a spin on Journey into Imagination with Figment and the gentle Living with the Land boat ride. She also would have fun coloring at the Kidcot Fun Stops around World Showcase, which also allowed her lots of time to run between pavilions.
I do truly believe that there is so much for your little one at each Walt Disney World theme park. Which park or parks you visit really depends on your preferences as a family. I suggest that you check out the
attractions with height requirements around Walt Disney World. This will show you so many attractions available without height requirements.
Please do let us know if you have any further questions, Gabriel!