The General (1927)

It' makes me laugh every time. Funniest thing I've ever scene

Definitely a movie to watch with the kids, who may need to understand some of the backstory (Civil war), plot, and some of the gags. In the first half of the movie, most of the action is on a train with Buster Keaton running over, around and up and down a moving train. The last quarter shows some warfare, but very rudimentary - shooting but no blood, people just falling down). It's still a very funny movie. It's worth going to the Internet Movie Database to review some of the movie trivia ahead of time - there are some fantastic scenes in the movie (train crash, etc) and information on these scenes are included in the IMDB (for instance, in some scenes actors were not warned about events that were planned and their shock on camera is genuine). We watched with a 5, 8, and 11 year old. All three loved the film.