Hi!!
I just thought of a vital item that I haven't seen on anyone's list!!
DRAMAMINE!!!
My oldest ds (11) is usually fine in the car, but when we put on a DVD and the car's moving...that's a different story. Will probably have all of us take a dose about an hour or so before we leave home.
I may even check into "the patch" for motion sickness, as well.
During our stay at WDW I usually take a Dramamine on the days that we'll hit the "wild" rides.
Have fun planning!

Deb