KOA Woodside in Bar Harbor. Cheaper than the oceanside, plus it's got full hookups throughout, wifi, and grass (if you're out back in the grassy area).
Saltwater Farm in Thomaston. Close to everything in Camden and Rockland, small and quiet, and mostly adults. Don't forget Owls Head while you're there.
Chewonki in Wiscasset. All grassy areas overlooking the salt marshes. Away from the hubbub (such as it is) on Route 1.
In Scarborough there's an adult only that looks good. Haven't stayed there as it's too close to home, but have driven through. Seems though the name includes Loon -- Laughing Loon or something like that.
Red Apple in Kennebunk is good.
Fred.