Can't go wring with a slaw or potato salad. There are salads with broccoli and ramen noodles that are pretty good too.
If you're looking for a hot side, mac 'n cheese is one possibility. In cooler weather I'd set it up in a dutch oven ready to bake and them bake on site. The cast iron will help to keep it warm while serving. (Or serve from a crock pot if you have electricity at hand.)