Nothing near Duck but there is a decent park in Kitty Hawk and on Roanoke Island which are closer than the ones down towards or on Hatteras. Still a long way to Duck so allow time for the distance and the summer traffic.
The Refuge has big back in slots with full hookups and clean bathrooms and a pool...as well as being on the sound side. Reservations needed in the summer so don't wait too long.
Refuge on Roanoke Island North Carolina 27954
Obx Campground is new and I don't know much about it but it does have full hooks and is right near the Wright Bro. Memorial in Kitty Hawk and would be the closest for you if available.
If you want to mix in Beach time with the wedding..suggest one of the two above for when you need to be close to Duck...then pick up sticks and head down to Hatteras for the beach time. Both of the above parks are within 10 minutes by car of the Obx beachesand the "strip" of restaurants & stores & recreation.