i'm thinking you can go the route of a picnic on the beach or bbq on the beach for inspiration

maybe chicken kabobs with veggies
if you can find a great sale on shrimp - get medium ones to kabob as well
or grilled chicken in one of those lime marinades from lawrys
you can have a fruit platter too
see if you can get a really good deal on fish- tuna or some other large fish. a half or a whole fish, or 2
grill it and serve it warm- you can marinade that too, or cook it with lemon, pepper and dill
have some pasta and potato salad as a side dish

i would serve punch too, a sherbet one and maybe a lemonade punch too, or a virgin sangria or that sort of drink
if you can get a blender you can make virgin margarita and other frozen drinks. (if you want to)