Hi,
if I were you, I would ask your students to write the screenplay. find a theme for the movie then divide your class into several groups: 1 group will think about the vocabulary/strutures needed, another will work on the characters (2 or 3 main characters + other characters), a 3rd group can concentrate on the setting, props, a 4th group will work on the scenes (3 or 4 scenes should be fine)
then write all the ideas on the board, and divide your class into small teams: 1 team will work on 1 scene. each member of the team will have a different thing to do: member 1 can work on character 1 (what he will say, facial expressions...), member 2 will concentrate on character 2... member 3 can work on the less important characters who will be involved in the scene, member 4 can work on the setting, the music, the props.
when all the scenes are finished, ask all your students to write the screenplay, correct the mistakes... (you can study a short screenplay to show them how to write one, use theatre screenplays, there are thousands on them on the internet)
i �m sure they will be extremely enthusiastic to know that they will write the screenplay and shoot the movie afterwards!
Elodie