Heading there again in a week... without the TT. The drive is really easy if you go I75, as stated avoid rush hour, Cincinnati and Atlanta are the ones to avoid on I75. We normally drive on the weekend and split between 2 days. We start the first days drive in the middle of the night and make it past Atlanta by dinner. The kids usually sleep until Dayton and night driving and crossing the border is so easy because there are no cars on the road. Than 2nd day is only about 6 hours drive. If you do Fort Wilderness with the park passes, meal plan etc, you can save around $1000 to $2000 vs a room at Disney. Fort Wilderness also has a boat dock where you can take the boat right to Magic Kingdom and avoid the hassle of parking, tram, Monorail/Ferry...
Fort Wilderness really is the Disney World of campgrounds :)