Hi Melissa,
My son just turned 4, and he's excited about going on ToT after watching the vacation planning video. He calls it the "elevator" and says, "It will be very scarey, but it will be lots of fun!"
Is he too young? He's not scared by stuff that most preschoolers are scared of. He's just under 40", but I think he'll be okay with shoes. How picky are they on the height requirement? I almost bought him a pair of girl Minnie Mouse wedge sandals the other day, just to make sure.