Gunfight at the OK Corral
Burt Lancaster is Wyatt Earp, Kirk Douglas as Doc Holliday. Earl Holliman as a Deputy, Dennis Hopper as Billy Clanton, and DeForest Kelley as Morgan Earp. Also, Whit Bissell (from Trouble With Tribbles) as the newspaper editor, Martin Milner (of Route 66 & Adam 12), Lee Van Cleef as Ed Bailey, and ugly one-eyed Jack Elam as Tom McClowery.
Kelley's part isn't that large I believe, but he's in the big showdown.
And then you could show the kids Spectre of the Gun.