If you are unsure if he will like it or not (too dark, too loud, etc) i would try to sit as close to the end of the isle as possible, this way if he won't sit for it and you have to make a quick get away you won't be in the middle of the row and have to walk in front of a bunch of others.
That being said, I have seen this with little nieces and nephews over the years and each of them has loved it since they were familiar with most (if not all) of the movies included in the show (Little Mermaid, Lion King, Aladdin, Beauty & Beast might be a few others that I am missing). The big issue for them were probably wearing the 3D glasses.