The DELMARVA seems to be an area little known by most RVers.
Come across from Virginia Beach on the 20 mile long, with 2 1 mile long tunnels, CBBT onto the lower DELMARVA. It is as flat as Florida but there is plenty to see.
Stop at Wallops Island NASA launch facility. Small but interesting museum there. Step back in time in Crisfield & stuff yourself with seafood. James Island SP for some spectacular sunsets over the marsh. If kayaking is your thing, Shad Landing SP on rt113. A little north, Assateague Nat Seashore for the wild horses & beach. In the middle Martinak SP near Denton. From here make a day trip to St Michaels & the excellent maritime museum. Eat more crab. Maybe go all the way down to Tilghman Island. Have to stop in Delaware for a little sales tax free shopping. Killens Pond S of Dover is a good one. The air museum at Dover AFB is worth a stop too. Smallish but much more touchy feely than the big museums.
That, briefly, is my area of expertise. All I can say about getting to Maine is to bypass Philladelphia, NY, Hartford & Boston as best as possible by going inland.