If he makes the height requirement and wants to give some of the rides a go, give it a shot! Our last trip my son was a few months short of his 4th b-day, we started w/ Goofy's Barnstormer... actual conversation DS (not yet 4) and DH
DH: "Did you like it?"
DS: "Daddy, this coaster was too short, we need a longer coaster!"
DH: "We can do that!"
So off we went to ride BTMRR and it was by far, his favorite ride of the trip, rode it 3 or 4 times. I've got a jr. coaster fanatic.

He's now hoping to make the height requirement for EE for our next trip, 'course he tends to mix up the
abominable snowman and call him the
adorable snowman!