We spend a week on the Outer Banks every summer. I've taken my bike the last two years, but I have to say biking there is kind of tough if you're looking to get any kind of distance in at all. The first summer, I was in training for my first century and tried to get in 30-40 mile rides. It ended up being a lot of back and forth riding, in one two- or three-mile segments, through the developments. Highway 12 is not an option at all. The shoulder is too narrow and there are way too many cars. It scared me to death the few times I had to be on it. So, you can get in a long ride if you don't mind riding in circles. As someone else mentioned, it can get kind of windy. There are some bike paths in various parts of the Outer Banks, but none of them were near where I was staying (Corolla, quite a bit north from where you're talking about) and weren't terribly long anyway.

That said, the Outer Banks are lovely and you'll have a great time there. I think you should go even if you can't get much riding in.