Good to hear from you. We flew into Boston & after a couple of hotel nights got over to Middleboro Cruise America depot by train from the South Station - good service, easy & quick. The depot is in the KOA campground, so we had a couple of nights there & went whale-watching from Plymouth - that was great! We drove up through NH, White Mountains & used KOA campgrounds most of the time. Their free wifi is a bonus! The Kancamangus Highway was brilliant but you may be too early for autumn (sorry, fall) colour. You may need to go further north into Maine for foliage, but there's plenty of help from tourist offices & various websites for up to the minute info. We came back down through VT - they said it was the best season for 20 years & what little rain we had was at night, so we were very lucky & had a fantastic holiday.
Feel free to get in touch again if I can help you any further.
Good luck & enjoy your trip