If conditions are good, ask to do some of the sites on the windward side of the island. Core Gut is a fantastic site. Other sites that are excellent are Man O'War Shoals, Diamond Rock, and any of the Tent Reef sites. Plan on doing some hiking. There are several great trails on the island, and you can get up-to-date information at the trail shop across from Sea Saba's office.
For restaurants, try Brigadoon and Chez Bubba for slightly upscale dining, Swinging Doors for barbecue, and Scout's for curry goat. Tropics has really nice breakfasts and the Hideaway, a fairly new place, has some interesting specials. And the Busy Bee for fresh bread, pastries, and coffee.