From North of ATL we take I-75 then the bypass around macon (I think it's called 475). Then the Florida turnpike to either 27 or I-4 (depending on which area we are staying in). "I" can make it in 6 1/2 hours without the 4 yo and the shortest with him was 7 (he slept most of the way so we didn't have to stop every few hours so he could strecth his legs) The longest was 8.5 hours with him.
We always plan to stop at the Ocala Welcome Center. Nice photo ops, legos for the little one to play with, clean restrooms, and just gets you excited.
We also stop at the Florida Welcome center (even though we just stopped for gas on the GA side of the border). The 4 y.o. loves to gather up his "maps" and look at them for the rest of the trip. Free oj plus we play in the grass (there is currently conctruction going on there so not as much play room)
Gas up/top off in GA--gas can be 30 cents per gallon more once you cross into FL.
We look for Chick Fil A and McDonalds that have indoor play areas and stop there. he plays while we eat and we get his food to go.
We take along a suitcase (going to Grandma's size) filled with coloring books, paper, books, small toys--like pvc figures, cars, fisher price people, etc., the Birbaum book for kids--even at 3 he loved to just look at the pictures.
We also have tv/vcr for the car but have only used it one one trip. And made 3 without it.
We listen to lots of CD's and sing along--Disney, Barney, Dora, etc. We basically turn over the CD player to him. He's now (at 4) at the age where he likes the read along books too.
Bubbles to blow and chase after at rest stops is fun. So is bouncing a big ball if you have room in the car. We've also done paper airplanes.
Hope this helps.