Paying non-certified

I did not know that uncertified staff who coach or supervise are supposed to get overtime if those hours exceed 40 for the week. We have many uncertified staff who take tickets at games, work the concession stand, or run the clock at games. They get paid a flat amount for each event. Unless they work multiple games in a week, I would bet that what they get paid is more than what they would get as overtime pay. I wonder if it matters how the pay for these extra hours is put on the books.