I was there last spring break around this time. We stayed in the Sea Pines plantation which is on the south side of the island. My buddies parents own a time share in the Mariot Monarch condo complex in there. It was right on the the beach and very nice.
IMO Hilton Head is a good place for a relaxed vacation. The whole island is pretty upscale, and there isn't a raunchy party scene like Myrtle Beach and places like that.
The one thing that drove me crazy was that it was impossible to find anything. The island has some law where businesses can't have tall signs or even lighted signs. It makes everything look nicer, but places can be tough to find.