Hi Gabriel,
What a fun age to take your son to Walt Disney World! I remember taking my daughter to Walt Disney World when she was a toddler. The magic in her eyes at that age was truly amazing. I suggest two theme parks for you: Magic Kingdom and Disney's Hollywood Studios.
Magic Kingdom is the place that most people associate with Walt Disney World, including Cinderella Castle. There are so many wonderful rides here for little ones, especially in Fantasyland. Your son might enjoy it's a small world, Peter Pan's Flight, The Many Adventures of Winnie the Pooh, and so many more. You can also
meet Mickey Mouse at Town Square Theater, which might be really fun for your son! Here, Mickey Mouse is in his magician costume. Also, be sure to take in
Dream-Along with Mickey, a fun show in front of Cinderella Castle featuring Mickey Mouse.
Next, consider a day at Disney's Hollywood Studios. In particular, I bet your son would enjoy
Disney Junior Live on Stage! in which Disney Junior characters, including Mickey Mouse, encourage children to sing, laugh, and dance. You also should consider a character meal at
Hollywood & Vine. For breakfast and lunch, this is Disney Junior Play n' Dine, with characters from Disney Junior including Doc McStuffins and Handy Manny. For dinner, you can join Minnie Mouse and her friends, including Mickey Mouse, for seasonal dinner parties. Please do note that characters are subject to change.
Please let us know if you have any further questions, Gabriel!