We stayed there over Memorial Day Weekend 3 years ago. Sites are tight, our neighbors campfire keep setting of our smoke detectors. Check out the reviews on RV Park Reviews.
We live on the Cape suggest the Bourne Scenic Park has water & elect. plus dump station then as y0u head out on the Cape Nickerson State Park in Brewster no hook ups but a beautiful state park. Then headed to Provincetown (the tip of the Cape) in Truro there are a couple of other campgrounds. Don't go to the one in Provincetown. extremely tight and noisey. Enjoy. We camp in these off season and travel in summer to farther afield (Alaska this summer)
Just one note if you plan on staying at Nickerson. It fills up fast so make reservations soon if you will be going in mid season. I suggest area 4.
Jim