A friend who manages a pharmacy has come up with a unique solution that might work for you. She broke the staff down into teams of four and told them what days and hours they needed to cover with two people working each day and no one working more than 30 hours per week. Then she gave each team a scheduling sheet and told them to work it out.
This is a great win/win solution. The manager is no longer “the bad guy” and the employees feel they have some control over their schedules.