There are quite a few good BBQ side dish recipes on this site, which you can find through the
LTHForum Recipe Index, including annieb's coleslaw (not creamy, but a nice variation), my Moroccan carrot slaw, pdaane's grilled cabbage, and a number of bean, rice and quinoa dishes.
I dunno about corn, watermelon or strawberries at this time of year, though. I think they'd be both expensive and inferior.