We've gone down every year forever, mostly not to disney though, but farther south - fort myers...we fly sometimes, but drive often. We've tried a lot of different driving options. Here's the highlights
1.) straight through (SW ontario-Fort Myers =22 hrs, orlando would be even less!!) Get up early in the a.m. and drive like crazy all day and all night - we drive in 3hour shifts during the day and 2 hours shifts at night. This is the best of the straight thru driving options imo as you start off well rested, and really by midnight you only have 6 hours left - 2 driving shifts for DH and one for me. Best part is when the sun starts to come up and you are there!
2.) straight thru option #2 - leave after supper and drive straight thru the nite, and then all day the next day. I HATE this method because you have been up all day packing, then up all night driving, then up all the next day still driving with your cranky kids who have not slept well...
3.) break it up into 2 days of driving, stay over one night (usually just past atlanta for us, maybe not even that far if only going to orlando) this is 2x 12 hour days really, but it's nicer than the all nighter imo, and less dangerous too.
4.) break it up into 3 days driving - this may be very relaxing, but you spend half your vacation getting there and the other half getting back...lots of driving, and the kids get cranky and bored. Would rather go straight thru than take this long to get there!
5.) FLY
we do this now whenever possible, in fact, we are headed out in 3 days and I am GREATLY looking forward to spending 2.5 hours on a plane instead of 25 hours in a van
When we drive, the kids love it if we wrap up little junky dollar store toys and then once every hour or two we let them unwrap one. Also we print off maps for each of them, and they can keep track of how far we have driven (this cuts down on the constant " are we there yet!") Would highly recommend the guide to I-75 booklet you can get at any bookstore, tons of fun facts that entertained the kids and also DH and I. Have a great drive!!!