Also, if you have a restaurant in mind, check their website, since they sometimes post online coupons. Capt. Anderson's is a good seafood restaurant, but usually no coupons that I know of. Cafe 30A (in Seagrove Beach, actually) is also good, but its more upscale than the usual PCB places. Schooners is another good location.
Does your brother have kids? They should do the pirate cruise if there are kids along. And Shipwreck Island Waterpark. The beach is gorgeous, of course, but there actually is some other stuff to do! Hope he has a great time.