We've driven to FL several times, gone different ways depending on weather and what time we are in certain areas. All have pluses and minuses.
We just came back from a 2 week trip, took I-91 south to I-84 west. Picked up I-81 in Scranton, then crossed over on Rte 17 in Northern VA to I-95. We left at 4:30am from north central MA and made it to Fredericksburg VA KOA for the first night. We were towing a 29 foot travel trailer and I am the only driver in the family who will tow that. The 8 yo and 9 yo had all kinds of DVDs, their own DVD player, pillows, blankets, books you name it. Still found that the only way they could entertain each other on this trip was to bicker and fight - first time in several road trips that this became such a problem.
From there, we went to Hunting Island State Park in South Carolina for two nights of camping right on the beach (had oak and palmetto trees at the site, lots of deer in the campground). Then back to I-95 and on to the Fort, arriving on Tuesday. The extra stops made this trip more memorable and enjoyable.
There is a big stretch of construction on I-81 in Pennsylvania between Scranton and Harrisburg. Down to one lane for miles. On the way south the traffic kept moving (Saturday), but we noticed a huge traffic jam for miles on the north bound side. Sure enough, same traffic jam on the northbound side two weeks later. We jumped off at mile 104 and took Rte 501 over to Rte 78 in order to take 78 to 287 in NJ, then 87 to 84. Rte 78 is also under construction with the traffic moving fairly well. The sections of concrete road that were not fixed yet on 78 were so bad and the timing was just right that the truck and trailer started to "porpoise" or get bouncing in a wave like pattern to the point where I was concerned that the hitch would strike the road (broke a piece of my Equalizer eventually). Also, we took a trip to NJ earlier this summer without the camper and took the Tappanzee bridge; there is still a lot of construction around the approach to the bridge and it was bad enough that we decided to avoid the area while towing. I find Rte 84 to be easier, less congestion and not much extra distance. Gas/fuel up in Port Jervis where the stations are huge and easy to maneuver; price is cheap. Not many gas stations on 287, none that I could see close to the highway.
Found a great campground with very large pull through sites, full connections right off exit 53 in Walterboro, SC. Name of the place is the New Green Acres RV park. Close enough to see the highway, so you will hear the noise, but not as bad as a truck stop. Has a pool, store, etc. and the full hook-up site was $26/night. Most of the business is from people who stop on the way to Florida. Lots of large shade trees, easy to stay connected for an overnight and yet still be level and comfortable in the trailer for sleeping. Very easy to maneuver and the place was about 1/3 full when we arrived for first stop on the way home.