12 Day New England Itinerary

Too aggressive. Keep in mind miles between stops up here means nothing-it's all about time. 40 or 50 miles can take 3 hours. You also aren't allowing near enough time to thoroughly enjoy yourself. You'll be spending more time cruising between sites than visiting. In answer to your questions, why do you want to go to Cambridge? I'd drop that and stick with Lexington and Concord, but if you take your time and truly explore you can spend a day at each place. Honestly I'd cut the number of places to visit in half. Acadia itself can easily be a day between things to see and do plus traffic. Kennebunkport is a good half-day, if not more. If you like to shop you can easily spend all day in Freeport. Boston? Days by itself depending on what you want to see and do. Make a list, prioritize, and then work it out. You will not do this area justice on that schedule.

Your best bet for Boston is to do it from Normandy Farms. There's little or no parking at T stations. You can't drive the RV in there-no place to park. Not sure what the other campgrounds may offer to access the city.