We spent a weekend at Beach Rose RV Park in Salisbury Mass on our way up to Acadia. The owner is terrific and helps everyone back into their site upon arrival. If you haven't backed in before this would be a nice perk for a first trip. It's also very entertaining
There's a bicycle path to the beach, and the town of Salisbury is small but cute. The campground is clean and well kept.
On the way back from Acadia we stopped at Wells State Park near Sturbridge, Mass. There are no hookups there, so it's dry camping, but it's beautiful and close to Sturbridge. Some of the sites would be VERY difficult to get into, but if you call and make your reservation on the phone I'm sure the ranger can guide you to an appropriate site for a trailer. LOTS of mosquitos here, bring OFF.