MA State Park - Great Choice
There are some wonderful sites in this campground, but not all of them have privacy. We really lucked out with getting one of a few sites left on Memorial Day weekend - after walking the campground, I think we would have chosen the same one again! #18 is right next to a ravine, so it was wooded on one side, and the two adjacent camps were visible but not on top of us. The trees are primarily pine, which made for pretty comfy tenting. Was a short walk to the facilities, but not close enough for the foot traffic to be annoying.
I loved that there were trails to hike from right in the park; you could do a short one, or a slightly longer loop (2.5 hours depending on your pace) with some inclines and boulders to scramble up and over. We were on foot, but it would be challenging for mt. bikers in some spots.