Atlanta is about 11 hours...but we don't use 75 when we go to Disney World...
We take I-77 to I-26...pick up I-95 to I-4, which takes you to Orlando...
The first time we traveled that way, we stayed in Rock Hill, SC...I do NOT recommend doing that! It wasn't a very nice area...
Twice we have stayed just above Charlotte, NC at exit 28 and it was a great place to stop and I was very comfortable staying there.
The area outside of Hilton Head and Savannah is around 12 hours drive and is also a good place to stop...
Hope this helps...