Husband and I were thinking of a fall
camping trip to the Cape this year. We haven't been there in many years and have never camped there. However, I was an annual Cape vacationer for probably the first 30 years of my life.
The only campground I am familiar with is Nickerson State Park in Brewster. From what I remember it's a very nice park. Well kept and clean. I only visited there, never camped. The only other campground I know about is the Campresort in Falmouth. Friends have camped there and had good things to say.
As for sightseeing - Hyannis is about halfway out the cape and has many shops and restaurants. Lots of Kennedy related stuff. You can drive by the "compound". You can also take a small boat trip through the cranberry bogs. Very educational.
If you drive all the way out , you will reach Provencetown ( or P'town) It's a fun place with lots to do. It is a very gay-friendly area, so if that sort of thing bothers you, you might want to skip it. Don't skip Nauset Beach though. It'd the best beach on the cape.
You can also take ferries to Nantucket and Martha's Vineyard. Both are fun places to spend a day. MV has clay cliffs and a lovely antique carousel.