We drove from Dayton Ohio (I-75 all the way to Fl turnpike) in January with DD 4yrs, and DS 1yr +2 wks. It was a great experience:
- we packed about 40 brown paper bags with small treats - food, toys, dvd, cds etc. every so many miles we would give them one, also if they misbehaved they'd have to wait.
- DS 1 slept most of the first day. I exhausted him the day before as well as sent him to bed later than usual.
-Moved DS's carseat by a window, he was fascinated
-The only nightmare was the hotel we stopped in the first night. He wanted to run around, we wanted sleep. Schlepping all the baby stuff to the hotel and back to the car not fun. I packed a special bag for the first night with all of our change of clothes in it.
-Bigger problems with 4 yr old, especially potty break needs. We controlled this by timing when we would give her drinks.
By second day the baby was ready to leave the car! Overall I would drive again. When DD was 3 we flew. We were supposed to leave Dayton at 12 and get into Orlando by 4. Reality, we got to the airport in Dayton at 10:00AM , and didn't get to our hotel room at POR until 1:00 am next day. Keeping a child entertained in the airports was beyond a nightmare. At least with driving we were able to have a car at WDW. If you are taking a full size stroller to WDW (which I strongly advise for 1 yr old's comfort and ability to nap) you'll be greatful for the car.
Have a great trip