I guess it depends on how good your kids do in long rides. We drove down last summer with the kids being 11, 8, 5 & 1. We didn't have the portable DVD players at all. Our kids did fine. We did have a gameboy though that I bought for the occassion and they all had to share it (except the baby). I think it's about 20 hours from here more or less. We split it up into 2 days.
I had Madlibs, search-a-word, magical coloring books (i.e. add water and colors appear to it - I got those through
AAA). I don't allow crayons or markers, so we use colored pencils. I also got little things - like I found these twisty ropes that you just keep twisting around and it is kind of curver, a Rubick's cube, etc... I had planned on giving them to them every couple hundred miles but it didn't really work out that way because they weren't all that fussy.
One thing I made up (read about it on these boards but don't know how to give credit to) was for my older 2 - I made up a 3-ring binder for the travels that included a map of each state with our route highlighted, information about that state (i.e. state capitol, flower, etc...) and then made up a find-a-word regarding it, had some pictures to color. I used a folder for each state (that had holes so they could be put in the 3 ring binder) and as we crossed over each state line, gave them the folder. They seemed to like that (the 11 year old I think enjoyed it the most).
We stopped at a rest stop to eat breakfast/stretch (we left around 3-4 AM - so it was a while later and we take a back-road for the 1st half - it's the first place to stop and will be a while before the next stop), Did lunch at a rest stop let the kids play on the playground there (that was probably our longest stop), then basically did some pit stops along the way but not too horrible. The kids slept a lot too.
For us, with a family of 6 - it was cheaper to drive even with the hotel cost than it would be to fly. Now, we don't need a rental car as we didn't mind using Disney transportation - so once we got there we parked the car and didn't need to move it again.