I agree with most of the above, but have a few things to add: don't forget the sunscreen! The fastest way to make a child miserable is to let him get sunburned. Make sure you rent a refrigerator at the resort (you need to call in advance and add this to your reservation). It costs $10 a day but you can store milk and other snacks in it for both of you. The fridges come with a freezer compartment large enough to hold two ice packs, so that you can take a smaller cooler bag with you into the parks and always have a cold drink of milk or juice for your son when he wants it (instead of having to find a place to get a drink and waiting in what could be a long line!)
Pooh and friends are also at the character meals at 1900 Park Fare at the Grand Floridian, which happens to be one of the best character breakfast buffets, at both breakfast and dinner.
With our little son, we would spend the morning in a park, go back to the hotel for lunch, and then spend the rest of the afternoon after a nap at the pool. This kept us all relaxed and happy.
Other great things for toddlers in the Magic Kingdom: Jungle Cruise, and don't forget Mickey's Toontown Fair, especially Donald's Boat. Forget Pirates and Haunted Mansion and Snow White-- too scary. Also Cinderells's Carousel was a favorite. Expect to ride Small World at least a dozen times! We had to ride it two or three times in a row every day!
Animal Kingdom is great for this age-- lots to see. Kilimanjaro Safaris is not scary in any respect. Walking trails to see the tigers and gorillas are also fun. It's perfect for a morning, and the character breakfast at Donald's Breakfastosaurus is fun. (Good food, too!)
Very little for this age at MGM, but you can't miss Playhouse Disney if your son know the Bear in the Big Blue House. Spectromagic is much too intense for a child his age, in my opinion--I know my son would have been terrified and I saw lots of parents leaving with crying toddlers during the show.
I don't know how long you are staying, but with character meals, the pool, and morniing visits to the parks, you have at least a week's worth of activities. Don't forget that when you discover an attraction that he likes, he'll want to do it again and again, and maybe every day-- and that takes up time. We spent 8 nights there and didn't see everything we'd planned (we also wanted to go to Typhoon Lagoon-- there is a great area there for toddlers called Ketchakiddie Creek, I think). There's also a nice petting zoo over at Fort Wildnerness, as well as pony rides-- and he might enjoy the Hoop de Doo Revue.
And don't forget simply riding the monorail-- a huge favorite of my son's. And the Main Street Railroad that runs around the entire park. I'd pick one popular attraction each day and try to be first in line for that and then take it easy from there (one day we hit the Tomorrowland Speedway first, another day it was DUmbo, a third was Jungle Cruise). That way you can avoid spending any time in line. As far as lines go, take a backpack with you and bring along some things he likes-- bubbles with a bubble wand are a great distraction in line. We also brought a tiny etch-a-sketch and he played with that too. At meal times we distracted him with other small toys we picked up along the way-- toy trains, a monorail car, etc.
Finally-- buy lots of postcards and/or a Disney commemorative book so that after you come home you can look at the pictures together and help him remember what he saw. We were there in April and my son still sings the Small World song and talks about Mickey's house and the castle. When he sees postcards of the fireworks, he says "Boom! Boom! Boom!" You'll have a great time. Check out Deb Will's web site (see the section on traveling with yound children) at wdwig.com. A good book is called Walt Disney World with Kids, written by a mom. HAVE FUN!
