Hi Emily,
How exciting to be planning not only your son's first trip to Walt Disney World, but a celebration trip as well!
Be sure to pick up a "Happy Birthday" button and a "First Visit' button for your son. These are available at Guest Relations at the theme parks, as well as at many other locations around Walt Disney World, and are free of charge. These will signal cast members and other guests alike of these special occasions. While there are no guarantees, sometimes a little extra pixie dust might be sprinkled on a guest wearing one of these buttons, such as a special birthday cupcake.
I recommend that you order the
Walt Disney World planning DVD. This is also available free of charge, and you can watch it at home. This may give you some thoughts on some of the best attractions for your son. I will share with you some recommendations that I have for this age range, but you might find that there are other attractions that he is really interested in due to his personal interests. Also, be sure to check out the website for
Walt Disney World vacations with preschoolers. This page has great suggestions for your Walt Disney World visit with your preschooler.
At Magic Kingdom, spend some time in Fantasyland taking in attractions such as Peter Pan's Flight, it's a small world, and The Many Adventures of Winnie the Pooh. At Epcot, your son may enjoy a ride on The Seas with Nemo & Friends and then taking in Turtle Talk with Crush. At Disney's Hollywood Studios, catch Disney Junior - Live on Stage!. Finally, when she was younger, my daughter loved a ride on the Wildlife Express Train out to Rafiki's Planet Watch to visit Affection Section at Disney's Animal Kingdom.
I hope that these thoughts are helpful for you, Emily. Please do let us know if you have any further questions!