Paula, I just posted a response to your AK questions. I don't know about timing,e tc....coul dbe tough, but I thought I'd give you feed back as to what your 2 1/2 year old might enjoy best on your list...
Playhouse Disney and Little Mermaid are must sees for toddlers/preschoolers!
Beauty and the Beast is great, if you like the music and the story (a lot like the BRoadway show - might not be great for the little one, unless he (I think you said little boy) is really interested.
Muppetvision is a good one for everyone. If he doesn't like the effects he can take the glasses off.
The Great Movie Ride is more entertaining for the parents -- not bad for kids but they dont know who all of the actors are and what the films are, etc....
The parade isn't anything really amazing, but it is FILLED with characters and cool cars. If your sweetie likes the characters, he will enjoy this. Then I would chose to see the whole parade.
So basically, if I were going with a 2 1/2 year old for the first time, I woudl be sure to see the parade, Play House Disney and The Voyage of the Little Mermaid. Oh, and the Honey I shrunk the Kids playground is cute and fun, too.
Hope that helps. Have fun!!