Lenny, sounds like you know his limits well and provide enough challenges to keep him moving forward. Exposing him to something terrifying probably won't help anything.

Is the cinema at a complex? Are they going by bus? Could you go with him on the bus, find something else to do with him while the movie is on and then meet up with the kids again for the trip home? Then he gets some of the camaraderie of attending the trip and isn't left out but doesn't have to see the actual movie.

for you, because it is tough and I am sure you will make the best choice for him.