We did something similar. As others have suggested, I'd save Canada for another trip. I'd also skip Philly and add DC. Stay at Cherry Hill RV park in Maryland and ride the metro into the city. The bus comes right to the campground. I'd give that three days minimum to see the National Mall museums and maybe a day trip to the Smithsonian Air and Space Annex at the airport.
For Boston I'd camp outside the city, we stayed at Wompatuck State Park which is south of the city. But you can take a short drive and catch a ferry to the city at Quincy I think. I'm not saying thats the best place to stay like Cherry hill is but it worked for us. The park was fine except that we had a heck of a time finding it. But I think we came in the back entrance. Unlike Florida which puts up plenty of signs pointing the way to it's parks, Massachusetts makes it harder.
Besides Boston itself you should make a trip to Concord and Lexington to see the National Park there. Thats a one day trip. I don't know anything about the whale tours
Acadia is an odd National Park instead of being mostly concentrated in one location it is scattered along the coastline in small chunks. We stayed at the Bar Harbor KOA which was good. You can get lobster delivered to your RV in the evening. Then take a drive up the coast to see the Schoodic Peninsula unit which is where all those spectacular photos are taken of the rocky wave swept shore are made. It is near Winter Harbor which is worth seeing. I'd give Acadia and the surrounds at least 2 to 3 days. Oh they have ferry boats tour out to the islands there, I don't know what the whale situation is tho. We drove up the coast almost to Canada as a daytrip to see the coastal villages.
One thing, DC and Boston are hotter than Hades in summer. So dress with that in mind and bring water bottles. Wear hats.