We took my nephew when he was five. He kept on saying he didn't want to see it, but we did get him to go, and he loved it.
That being said, he was a bit scared. I purchased one of those Mickey lights for him, and I told him it was a magic light, and if he got scared, to turn it on, and Mickey would help him be braver. The light did the trick, and he did hold it up a couple of times, but over all he loved the show, and it's one of the favorite things he did on that trip.
I guess it really depends on the kids, and you know your kids the best.
Karen