M.6.
I'd go - I've taken kids/grandkids at that age and sometimes it goes great, and other times not so much (which can be the case of kids even older than that!). Sit in an aisle seat for ease of getting out to the door if needed. I always it closer to the front since the kids seemed to be more engaged in the movie if we were closer to the screen, but that is totally up to you. If you go close to nap time, you might find that he ends up dozing off after awhile. Bring a blanket and a lovey if that helps.
Good luck!