You might want to consider the Amtrak car train from Lorton, VA to Sanford, FL

I agree with the above about your potential for nightmarish traffic through the NYC area - I do that corridor fairly often when visiting family and even though it's more miles, it's less time to do:

90 to 84
Danbury get on 684 South
Exit 5, Saw Mill South
Take 287 to cross Tappan Zee Bridge
Continue on 287 to 78 West
Follow 78 into PA
Near Harrisburg take 15 South
Follow to Fredrick, MD
Take 270 South
Take beltway 495 toward Virginia/Tyson's Corner
Take 95 South

If you opt for the car train, Lorton is off 95, just south of Springfield, VA (the "mixing bowl" area)......that point is 500 or so miles and will take you, if you time it perfectly for traffic, about 8 hours.

If everything goes well and you have smooth sailing (often the case going through Danbury then over Tappan Zee into PA via 78) you can be into Lorton for the auto-train same day as you leave Boston. But, you have to leave Boston no later than 5:00 AM - with stops you can pull into Lorton by 2:30 and make the train's last auto time of 3:00.....but you'll be cutting it very close if you hit any traffic or construction delays.

What may work better for you is to leave Friday after work and rush hour - get to between Danbury, CT and Ramsey, NJ - stay overnight and start your morning from there and catch the auto-train in Lorton.....less room for time errors.

I'm suggesting the auto train since it departs at 4:00 PM and you travel overnight, arriving in the morning (I think around 9:00 AM) well rested if you get yourself a family bedroom! A car for the train is less than $200 - and saves you the driving!