It's a very, very nice place. Hard to go wrong there. I grew up going every year. You basically have beaches, golf, bikes, and a few nice places to eat, so don't expect Myrtle Beach. But if you want to get a break from the madness, it's a great place to go.
As far as places to stay, if my memory is correct, your cheapest option will probably be along South Forest Beach, which is public access, but still not terribly crowded. It's also convenient to most of the island. Once you get into the plantations, you're not going to stay oceanfront (or really anywhere) very cheaply. But almost everything is nice on the island.
If you go, make sure to visit Harbour Town, Shelter Cove, and the Old Oyster Factory. And, of course, you have to buy a Salty Dog Cafe T-Shirt, even if you don't eat at the restaurant
