This one!
Bald Head Island, if you are looking for quiet and away from crowds. We used to rent a house there every year when the kids where young, mainly because it is so secluded that the we had no kids worry. Only bikes and golfcarts on island. If you have never been there its worth a visit. What we did is waited until October and rented a house for a long weekend, rates go way down by then. That way we tested the place at a reasonable rate. Kids and wife loved (I hate beach) so we rented there for 10 years in a row during summer time.
Very quiet, you can be on the beach and see a dozen people, walk for miles and see no one, and there is a lot of fishing on the frying pan shoals. Not the place to go if you are an extrovert, the lack of sounds will drive you nuts.