Another good spot for off road beaches is Carolina Beach. Spent a many weekends there as a local.
Check out Freeman Park (north end) and fort fisher. Freeman park is a pretty good time. Park your truck, pitch the tents, start a fire, drink beer, dog friendly, and throw some lines out in the water.
Gets really packed on holiday weekends... almost turns into a two lane beach, giant party. Any questions, let me know!
Damn I miss NC.