You'll want the board game to include things that will never "go out of business". So, restaurants and shops would be tricky to include because anything could happen to them (go out of business, change names, burn down, not get leases renewed). Communities such as Rosemary Beach, Alys Beach, Seaside, Grayton Beach that are so well known would be good. Also, general types of stores and shops (e.g., pizza place, art store, ice cream shop, etc.) would be good and the design could reflect the establishment they are thinking about without actually giving the name. So, if the place name changes, the game doesn't go out of date.
For game pieces or cards or challenges, the kids could use turtles, frogs, Monarch butterflies (skip the dog flies), gekkos, beach flags, dunes, pools, etc. It would be great to be able to teach people about the flag system or "stay of the dunes" or "turtle habitats" (without getting overly preachy of course since it's a game). The beachy things I think of are sunsets, beach chairs, beach toys.
They must be having so much fun thinking about these things.