I think the Twas the Night Before Christmas show in the Galaxy Theatre would be good and it is near Buzz Lightyear for a quick ride before or after. Also, the dance parties might be fun for a child that age and the since different characters seem to come & go it might make for some good character interaction. The Castle forecourt show might not be as appealing since the characters are higher up if you are close to the stage and farther back might not be a great view for the little one.
I would say the parade would be great, esp if you are on the front row, the scents from some of the floats (pine, cookies, gingerbread) are delicious! Also, the Belle show might be a good choice since it is a smaller group and your child might get chosen-not sure if they'd like that or not though!