She may end up sleeping through majority of it. Take some breaks to stretch and if your car has a movie system play some movies if not you can get those DVD players that hook up to your head rest.

We did a 18 hr drive from ok to Florida lots of stops that’s all I can say and start at night

Is it possible to do an overnight drive? The longest I’ve driven with my kids is a little over 300 miles and they tend to just sleep in the car.