I have done this 3x now from Ontario, Canada. Twice with just adults and once, last October, with our kids who were 5 and 7. My DH and I took turns driving, about 4-6 hours at a time and we drove straight through. It took 25 hours. We were expecting it to be pretty hard on the kids but we didn't have any problems at all and it was actually quite enjoyable.
We decided before we left that we would stop for the night if we felt the need to. We never did and we felt fine - not overly tired because we took turns sleeping while the other drove.
We left at 10am and got to Disney at about 11:30am the next day. When I went to check in, I requested a room that was ready. They were very accomodating. I urged everyone to rest since it was a free day with only dinner reservations but we just couldn't - instead we watched some TV for about an hour and then had to get out - had a late lunch, rode the monorail around to all the resorts, went back to the room, got ready for dinner and headed to Chef Mickeys. In the end, we would much rather drive straight through and have a lazy day at Disney rather than spend 2 full days on the road.
I read lots of tips on this board but mainly the things that worked for us were...
FIRST AND FOREMOST: Set the kids expectations that this is going to be a LOOOOOONG drive - for us, a whole day and a whole night - we kept reiterating this before we left. Our kids were both old enough to understand and it really helped. We didn't get a single " are we there yet?" until Georgia when the kids woke up in the morning.
1. watched a few movies on the DVD player (we really didn't feel like we had a lot of time for this but I am glad we had it for the times we did use it)
2. If possible, stop at a fast food place with a playland - eat while the kids play and get the kids food to go so they can eat when you are back on the road.
3. took the Leappad which covered the US states we were driving through and had many other activities too
4. Gave the kids journals and they wrote down all the cool things they saw. We have fun reading these today ("drove over bridge to USA" "saw rock mountains" "saw a palm tree"). I answered a TON of "how do you spell...?" questions
5. We followed the same bedtime routine we would at home (as best we could). At 8:30, we stopped at a rest stop, kids got their jammies on, brushed their teeth, used the loo, and then we read a story and tucked them in. They slept right through and woke up at about 8:00 in the morning.
When we go back (my DH says "IF"), we will definitely drive again and we will try again to do it straight through.
That's our story,
Kelly