There are still a few things to think about though. Even if you have soft drinks, you'll still need water for the volunteers. A grocery store may contribute bottled water, or just get everybody you know to fill their coolers with ice water. This one is a tough call. Some people like quiet, and some people like to move to the music.
Some people are a little bit country, and some are a little bit rock and roll.
Play it by ear. Who knows, you may be able to talk a local freelance DJ into providing entertainment in exchange for a sponsorship position. Advertising is a wonderful thing. Look to your sponsors for these things. You get the idea.