Let's see...I love the beach, and I would think a boardwalk them would be fun. The food that would be appropriate - french fries, pizza, snow cones, ice cream, lemonade. Boadwalks always have carnival type games (basketball throwing,e etc.) , and arcades. Seagulls and shells for decoration. Being from New Jersey, we have beach tags here, so maybe you could give everyone a tag. I don't know how elaborate you get, but I can see how fun this can be! Good Luck!
My kids once attended a day camp in the summer with a similiar theme. It was done by teachers. They had the Hawian spot. They told a little history of the Islands and taught the alphabet and some words. It was VERY interesting, I learned alot. They were in pre-k and kindergarten and they enjoyed it too.