Welcome. If you're looking for rural Florida, check out the panhandle/Gulf coast. Several nice city, state and private campgrounds and RV parks and not as crowded as the south of I-4 area. We spent 6 months on the road last winter and thoroughly enjoyed it. We used the old US route system wherever possible. Much more relaxing.
I like I-81, but depending on the time of year you make the trip, you may want to cut back to I-95 south of DC. Watch the weather. You can grab US50 or I-66 to US17 and re-connect to I-95 north of Fredricksburg VA.