Clean up styrofoam peanuts ALL over the yard?

First see if they are really styrofoam. Lots of the packing peanuts today are organic- made from potatoes. But they look like styrofoam. Put a couple in water and see if they break down. If they do, just spray the yard with water. If they just float and don't break down- yep, styrofoam. So you'll have to rake them all up or hope for strong wind to send them down the road.