I'm not familiar with rental houses because my stays there have been in B&B's, but I'd suggest looking into NC's Ocracoke Island. It's lovely, isolated and quiet with beautiful beaches. And kids (or those who act like them on occasion) can enjoy exploring some of the old haunts of colonial-era pirates, including Blackbeard himself. (He met his end at the hands of the Royal Navy when they found he and his crew anchored at Ocracoke.)