Wow.. no hot dogs at the beach.. bummer
Well, you could do a traditional Chicken picnic. Fried chicken, potato salad, coleslaw, macoroni salad, baked beans, chips, cake... and a side of rice krispie treats.. gotta have the treats at the beach! Large coolers with block or dried ice work great. Separate the drinks from the foods. That way, people can get drinks without disturbing and decreasing the cooler with food.
Salads can be put in those bowls that come in two parts. Freeze one section, food in next section. Those can be found at gourmet shops.
You could also do a Mexican theme....... complete with a graduation pinata!
Enchiladas, burritos, taco's(ingredients in a section dish)Rice, Beans, Salad, flan, cake... hec I might even throw in those Rice krispie treats..

Chips, Salsa, Guacamole and veggie plate too.
Most of the above can be ordered, or homemade.
Congratulations on dd graduation!