Hi Roseann! I just returned from a vacation with my 3 year old grandson and he has been joining us since he was three months old! With each visit he experiences new things and enjoys the old ones even more.
Make sure he gets to some character greetings or make an advanced dining reservation for a character meal. My favorite is Chef Mickey's in the Contemporary resort. Another great spot is the EPCOT Character Greeting which is to the right of the big fountain in Future World. At these locations you might see all the main Disney characters like Mickey, Minnie, Pluto, Donald, Daisy, and Goofy!
Don't hesitate to take him on rides that you feel are beyond his age. He will enjoy many things in his own way and can learn from observing. You can click
HERE to reach the Disney site for the attractions and then click on RECOMMENDED AGES on the left side. Check his age grouping and you will then see a nice listing of the rides and attractions that Disney feels is age appropriate. You can plan your days in the parks using this list if that helps.