My big advice is to pick one route south and a different route north.
I didn't catch how much time you have, but add a bunch of time to that so you're not disappointed.
DelMarVa peninsula is neat and it will get you the tunnel/bridge if you want, but be aware... It is remarkably rural. Those yellow lines that look like highways are 45mph 4-lane boulevards with stop lights. There are sections of some of them that are now real highways, but if you are looking to shave time, DelMarVa is not the way. If you're looking at seeing sights and doing things, it's fantastic. Tons of kitchy roadside stops. Tunnel and bridge are neat, but one of the neater things (I think) is the Cape May-Lewes ferry.
The I-95 corridor (my opinion) is something that should be avoided north of Richmond and cherished south of Richmond. When I go from PA to FL, I usually take the 81 corridor down to 77 down through Charlotte to 26 which meets up with 95 north of Charleston. That keeps me out of the craziness of I-95. It adds a hundred miles or so, but often shaves a couple hours off. It also keeps me inland enough that I'm in mountains. It also puts you dangerously close to Blue Ridge Parkway and Skyline Drive.
If I were doing it, I would take the quick route down and the slow route back. My personal choice. 81, 77, 26, 95 on the way down with jaunts over to Skyline drive and Natural Bridge, then on the way back, 95 up to just south of Richmond. Cut over to VA beach, take the tunnel, up DelMarVa, Cape May-Lewes ferry, then rejoin 95 north of Philly. You'll go up past NYC and get some traffic, but honestly... it's not as bad as Richmond.
Whatever you do, I strongly recommend on one of the legs that you experience Savannah GA. Amazing town. Also, the spread from Jacksonville to Ocala on 301 is, um... painful. Anywhere from 35 to 55 mph, stoplights, etc. You should experience it on the way down and then decide if you want to do it again on the way north. I don't know how to describe it. It's like one part banjos, one part pirates of the caribbean, and one part 1965. You're not sure if you'll be attacked by zombie armadillos, or break down in front of a voodoo gift shop. Either way, you'll probably get pulled over for speeding if you don't religiously watch your dash. 301 from Orangeburg SC all the way down to Ocala is a real journey of WTF. I think everyone should do it once. Once. I've done it about 20 times and I still don't get it.