Best route

I would never go as far up I-95 as DC....1st problem is construction day and night starting below Quantico, VA. I travel this often and it sucks. Hit I-26 in SC and take it to I-77 up to I-81 in Virginia. At Scranton, PA jog a little South on I-380 and then pick up I-84 East (North?)Part of this is Mass Tpk. to I-90 to I-495 to exit 30 Littleton......You won't be sorry as you miss all of the BIG city hassles and most of the tolls other than Mass Tpk. Be aware of the weather in the winter but Interstates are usually open even in the worst conditions. I have made the trip both ways, I-95, and it might be longer in miles but its shorter in time and agreivation.

X2 on I-81. Go up I-95 and take the I-495 beltway around DC. Go up to Baltimore and pick up I-695 around Baltimore. Get off I-695 at the I-83 north exit. Take I-83 up to Harrisburg PA and get on I-81. Take I-81 into Scranton PA, then pick up I-84 east. You will by-pass all but 1 toll in Port Jervis NY. It cost me $5.00 to cross in a 40'dp with a car on a tow dolly. If you want you can then take I-84 through CT and right up to I-90 in MA.

The northeast corridor is loaded with toll roads. By going this way you will by-pass all but one toll and its a cheap one. The milage is more but the lack of tolls and better scenery makes up for it. Two years ago the Tappenzee Bridge cost me $25 to cross. Go a little farther north and pay $5 to cross the same river.

95 26 77 81 78 287

A lot of folks work their way north on I-81 to avoid DC and NYC area.

We are leaving from Port Charlotte, FL for the trip to Massachusetts.

It it were me (and it's not!) I would take 95N all the way to the NY area (495 around the DC area) and then go as far around NY as possible. For me, that would mean 95N to 287 to 287/87E to 684 to 84E. Catch 90E to 290 to 495 and in.
Use Google maps and move the route to match mine or compare some of the alternate routes. Just don't select the default route with 95 all the way. I did that once as a rookie and it was a very scary experience. You could also take 87 all the way up to 84 for only a few more miles but easy of transit.
Not knowing your actual point of departure, it would seem that Jacksonville would be your first stop followed by Florence, SC, DC area, check out Cherry Hill, somewhere around Danbury, CT and then into Littleton.
Check out RV Parky and/or rvparkreviews to find a park along the way that works for you.