re: Taking a 3 year old to Disney World?

It's really kid specific. We just got back and my son turned 3 while we were there. He loved seeing the characters even though you couldn't interact with them like you used to be able to.

But to see the pure excitement on his face riding the seven dwarfs mine train and slinky dog dash was something I'll always remember. You'd be surprised at what they can ride that young. Like I said, ours turned 3 on the trip and was just at 38 inches. A lot of the bigger rides are 40 inches, so if yours is closer to 4 or tall for a 3 year old, he may be able to do more than you think.

ETA: I just looked....if your kid is 40 inches they will be able to do every ride except Space Mountain, Rock-n-roller coaster, flight of passage, and everest.