We took our DS to MK on his 2nd birthday. He was a little clingy in the pre-show for the Haunted Mansion, but actually fell asleep on the ride. We were at DL a few months ago, and he was two weeks shy of his third birthday. This time, he got pretty scared during the pre-show. He started to cry while we were walking to the ride portion from the stretching room (I believe you ride through this portion at MK). A few calming words and he was ok, but I would be prepared to exit early.
As far as the rest of the park, at MK when he was turning two, he didn't enjoy too many of the rides. He didn't cry, but he closed his eyes on most. He did like Winnie the Pooh, Buzz Lightyear and Its a Small World (of course).
At almost three, he enjoyed most of the rides he was able to go on at DL. He particularly loved the Teacups. (no extra spinning...) He liked Peter Pan, Mr. Toad, Country Bear Jamboree, the DL Railroad, and the parades.
OH, we have the
Disneyland Sing a long video tape, and he LOVED watching it before our trip to DL. There's a song in there called "Walkin' Right Down the Middle of Main Street USA". When we went to DL, he pulled me over to the middle of Main Street and started singing the song while we walked down Main Street. AWESOME!
He napped in his stroller, so we didn't need to leave the park for that. He walked about 1/3 of the time when he turned 2, and almost all the time when he turned 3. Parking and picking up the stroller before and after each ride was the only hassle, and that's not too bad. Besides, if he's walking, the packages go in the stroller while we walk...