The McKee Memorial Reserve is an awesome camping spot on the edge of Tasman Bay. It's one of the few places where you can camp right beside the sea and be at one with it day and night. In fact on a really stormy night, I have a feeling you might be a bit TOO close.
The facilities are fairly basic but the fees really inexpensive. The cache is near the start of the reserve so you don't need to be too worried about the fact that the gates are locked at night.
Do park considerately and safely and look after young children near traffic.