Hi Suzie:
I'm a parent of two boys, ages 5 and 4, who have been traveling to Walt Disney World since they were infants. In my opinion, three is a perfect age to bring your son to Walt Disney World. He will likely enjoy the experience, and
you will always remember it . You can capture parts of the trip through pictures and video that you can keep and share for a lifetime or longer.
Your son will likely nap in the afternoon. We visit the Parks first thing in the morning, head back to the Resort after lunch for nap or pool time and then head out to dinner. I would love to share some of my family's must-dos for our Disney World vacations. Your family may have different tastes, but hopefully these recommendations will be a good start to planning your trip.
Among many other things: at the Magic Kingdom, we always ride the Jungle Cruise, Peter Pan's Flight, Mickey's PhilharMagic, and it's a small world. At Epcot, we take in Spaceship Earth, Living with the Land, and tour the countries of World Showcase. Our must-dos at Hollywood Studios include Toy Story Mania and Muppet Vision 3-D. At Animal Kingdom, our family always rides the Kilimanjaro Safari and visits The Boneyard and Conservation Station. Of course, every family is different, and to have a successful trip, you will have to take your son's likes, dislikes, and comfort-level into account.
Also have a look at Disney's in-depth planning page for
traveling to Walt Disney World with younger children. As you enter the parks, pick up a Times Guide for parades and show schedules throughout the day. During your visit, you can't go wrong with a character meal, particularly at Chef Mickey's.
My best advice is to relax, follow your son's pace, and enjoy.