Deadly Sunday (1982)

A family on vacation stops at a roadside restaurant where a gang of criminals are holding the employees hostage. When one of the hostages tries to enlist their help, the family is added to the group. Disagreements on how the hostages should be treated leads to dissent among the criminals, who are awaiting the arrival of their leader. (The leader, for unexplained reasons, has all the stolen money.) Some hostages are killed; when the leader arrives, the hostages overpower them and free themselves.