Christmas Eve itself will probably be kind of quiet. But earlier in the day I think you can expect heavy traffic on I-75 in Georgia and Florida and then again on Florida's Turnpike. That's a Sunday this year which means anyone from the midwest that is coming down for Christmas week probably hit the road on Saturday, spent the night somewhere enroute Saturday evening and plans to finish the journey on Sunday. My guess is it's going to be crowded out there.
But if you plan to be at Disney by 12 noon or 1pm then you'll be ahead of most of the traffic as the afternoon is usually the worst.
One of the biggest backups (usually) is the mainline toll plaza on the Turnpike. That can back up for 2 miles on holiday weekends. Check the map and you'll see that there is a junction for US27 on both sides of this toll plaza. So if there is a bad backup and you can get yourself off, exit at US27 and proceed south and in a few miles you'll come to the other junction with the Turnpike where you can get back on southbound. Going around the mainline toll plaza does not save any money. The mainline toll is $2.50 and if you get off they'll charge you $1.25 getting off and another $1.25 getting back on. But you do save a lot of time versus remaining in the back up. And US27 runs parallel to the Turnpike so you're not far from it.
BobK/Orlando