You asked for things to do and got a lot of suggestions, I'll add the following.
- If you find yourself on Hatteras Island, take the family to the UFO House. It's fun. And weird.
- Graveyard of the Atlantic Museum is worth a visit. It's not large, but you can learn about the lighthouses, the Fresnel lenses, pirates, and shipwrecks. Free, donations encouraged.
- Soundside sunset kayaking. Many places offer guided excursions all up and down OBX, these are great for families and sunsets over the sounds are pretty dang good.
- Jockey's Ridge/Wright Brothers Memorial. Aside from acknowledging the greatness of 2 Ohio boyz, the sand dunes are crazy high (and fun) and there are some walking/hiking trails.
- There's no shortage of wind/watersports, if you want to try any. KHK is a good reference and very reputable, but they are not the only outfit: Outer Banks Adventures and Activities | Kitty Hawk Kites - https://www.kittyhawk.com/adventures/
- Pick up a 2-line stunt kite. I'm in my 50's and love flying it (and trying tricks): I had my nephews try it this trip and they both went home with their own kites.
Do you have the gear to make days on the beach bearable? A lot of people swear by awnings, but I've seen more packed up due to wind than deployed. We got a Neso Sunshade (
Beach Sun Shades and Portable Canopies by Neso Tents - https://www.neso.com/) and it was amazing, it was the first shade we could put up early and not worry about all day. Next investment for me is a CGear Sandmat (
ORIGINAL SAND-FREE MAT - https://www.cgear-sandfree.com/products/original-sand-free-mat) as I hate having sand from towels, other mats fill the vehicle, garage, washing machine.
Doing any fishing?