Hi Sharon! I lived in NC for the past 7 years and my very favorite place to vacation are the northern OBX beaches. My boys are 9 and 7

. I've never used homeaway for a rental place but rather a company called Kitty Dunes Realty.
The first year that we vacationed there was the first week of September and unfortunately we were there during the time that a tropical storm was rolling it. Water was rough and cold. I've been in June, July and August as well and had great weather so hopefully you'll be fine!
When researching the OBX you'll see that there are numerous towns listed, Kitty Hawk, Kill Devil Hills, Nags Head, etc. Those towns really all run into one another with little differentiation as to when one stops and the other begins, so don't let the name of the town deter you from renting an otherwise great house. The towns of Duck and Corolla are a little bit further out. There are areas that direction that are ONLY accessible by a 4WD vehicle, no paved roads, no grocery stores, nowhere to eat out, et cetera. Avon is considered the OBX as well but is really far out and there's little to do out that way other than the beach, so I'd personally not recommend that unless that's what you're looking for.
The towns of Kitty Hawk, Kill Devil Hills and Nags Head (and possibly the other towns too, just not 100% sure) all have beach accesses with parking lots every few blocks, we've never stayed directly ocean front, way too expensive and even though we usually stay close to the ocean, we have way too much stuff to lug, so we load up the car, drive the couple blocks to the ocean and then settle in for the day. Some of the beach accesses have showers and bath houses, some of them are more basic. Check out this website for a list of life guarded beaches and their offered amenities, sorry i can't post a link but its outer-banks dot com. Pets are allowed on some of the beaches as well, some of the beaches require them to be on a certain length leash while others have no leash regulations.
As far as things to do... there's tons! Your boys may like to check out the lighthouses, you can even climb the one at Cape Hatteras... be forewarned, it's a long climb, in a tight space with lots of people but it is so cool once you get to the top. There's an aquarium at Fort Fischer which is a little small, in my opinion and since we've been a couple times, we now skip it. Jockey's Ridge is a huge sand dune and really neat!
I sure hope this helps, let me know if you have any specific questions once you get into planning your trip a little more!