Outdoor lighting for our wedding reception?

My Fiance and I are having an evening reception August 6th in Indiana. Our venue is a very NICE school with a huge field in the back and a gymnasium that we could also use, but we love the thought of dancing and celebrating under the open sky-so we're trying to stick to outdoors! Now, the field in the back is humongous! like 2 or 3 soccer fields, with a half-mile sidewalk around the edge. My only dilemma is lighting! So, I am in need of some really creative *inexpensive* lighting ideas! we can get electricity through a generator and extension cords. i just need help figuring out how i'm going to light this place when there aren't any trees around. Ideas? Be as "out there" as you want, and i'm willing to craft together some invention, i just need ideas. Thanks!