Lived in Beaufort for a couple of year and still have family in the area. These are my must eats when I visit.
Back porch grill: at port royal marina: terible service (not rude just slow), great views, not on the menu but if you ask they make a killer blue cheese tabasco burger

, oyster po' boy is awsome too. Best bloody marry's. This is my usual go to.
Dockside: port royal, best seafood hands down, good views, dont know if they do lunch
Alvin Ords: Awsome sandwich shop, turkey salvation on french bread

, local favorite.
Nippys: downtown pretty good seafood
Blackstone: If your there for breakfast best on the island, never been other than for breakfast
Shrimp shack: not sure if they are open this time of year and it is a bit of a drive out to the end of ladys island: shrimp burger.
Upper crust: pretty good pie
Have fun!