M.P.
I think you should just take him and see what happens. He may sit quietly or he may scream his head off through the entire movie, however the more he goes and is exposed to that particular setting, the sooner he'll learn how to behave at the movies. I take my kids all the time...my 2 year old son has learned to sit still ( on my lap anyway) and my 3 year old daughter is ok as long as she has a juice box and a snack. The point is put him in the situation and see how he does. most moviegoers are understanding of an active 2.5 year old.