C.M.
You can stuff them with just about anything, leaves, hay, newspapers, cotton batting, etc. I would definitely make some themed ones, like cheerleaders, teachers, football players, etc and stage them. Also, try to make the faces very recognizable with paint and even add wigs. I'd also make some standing, some sitting etc just for the variety. I would also decorate the area the scarescrows will be in. Hay bales, corn shocks, pumpkins, some fall mums, etc.
Have fun and hope you make lots of money for the fundraiser!