We stayed at Pinewood Lodge a few years ago and really liked it. Very near to Plymouth. When you visit Plymouth Rock, make sure to talk to the Rangers there - they give a very good and informative talk about it.
We stayed at Atlantic Oaks to visit Cape Cod, great campground. The pull thru sites in the back half of the campground are surprisingly spacious and well laid out. If you like bike riding, the campground is directly connected to the Rail Trail - beautiful, flat, and scenic paved bike trail (old railroad right of way) that runs the entire length of Cape Cod.