We drove from Chicago to WDW with a 15 month old, 3 year old, and almost 14 year old (plus mom and dad), in a minivan. It's like 20 hours non stop, but we stopped alot.
We left Chicago at around 4-5am and would stop around every 2 hours. We made it to the Nashville area around 5pm. We stayed in a hotel with an indoor pool.
We left Nashville around 6am and got to our hotel around 8-9pm.
I had lots of new toys I bought the kids that I was saving throughout the year. I would give them each a new toy every couple of hours. These were small toys...nothing too extravagant or complicated.
We didn't have a vcr/dvd in the car and I wish we would have gotten one.
We are going to WDW again in a few months and I am borrowing a friend's vcr for the car. I figure we can watch a movie, then make a quick stop to stretch out. My 2 youngest are now 4 and almost 6 and they are still in car seats/boosters so they really need to get out and stretch their legs.
If your children are well behaved in the car, then I think driving will be fine. Just make sure you get them out of the car seats every couple of hours. Map out where the rest stops are so they can get out and run around for a bit. Maybe even try to plan lunch/dinner at a McDonalds that has a playarea so they can really climb/jump/run.
Of course you want to pack lots of snacks for the trip. And what helped us was we had all of our luggage in the luggage rack (in one of those luggage holders that attaches to the rack), but we kept one small suitcase in the back of the van with our swim suits, pjs, change of clothes for the overnight trip. We left all of our luggage locked in the luggage holder overnight and it was fine.
Have a great time.
Mary