Hartlawnmain, I think that 80 sq ft per bale is spreading it pretty thin. I know with 1 cubic ft of mulch spreading it 3 " deep will do a 10 X 10 area....2 " deep will do a 12 x 12 area. With pine needles, with that much square footage, I'd estimate 160 bales covering a 5 x 5 area.
Someone else might have other ideas, that's just mine. Good luck.