As you are aware, several good courses nearby, but courses fun to play by a 6 year old, less so. We go to Sunset Beach regularly and an option a few have used for young golfers is the par 3 course just across the state line in Little River (SC), unable to remember the name. It is on the West side of US 17. Also, at least from the way it looks from the road (Hwy US 17), Valley at Eastport Golf Club might be what you seek for a young golfer. It is across the street from the par 3. I am assuming desired course attributes to avoid for young golfers: forced carries over water, deep bunkers, fast undulating greens, etc, Most courses offer quite a few sets of tees, so choose a set to make sure the young golfer has fun. However, if you are willing to play courses with such characteristics; the nearest course to OIB is Rivers Edge a nice Arnold Palmer design. If you venture out towards Sunset Beach, a few good courses well worth playing and you never leave NC. I especially enjoy these during summer weeks if I get a tee time before 7:30AM, then I am back at our beach house and sitting on the beach by Noon to 1pm.
1) Sea Trail (3 courses: Maples, Byrd & Jones)
2) Oyster Bay
3) Sand Piper Bay (3 nines)
4) The Pearl (3 nines, 9 holes closed Jan 2020)
5) The Thistle (3 nines)
6) Ocean Ridge Plantation (4 courses: Panther, Lion, Tiger & Leopard)
7) Crow Creek
Meadowlands
Hope this helps and have a great vacation.