Cheetos are the most critical thing for a pleasant road trip.
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Seriously though, I would say some audio books for when you get bored, and also some camping or hotel guidebooks from AAA would be helpful. Figure out roughly how many miles you want to put on in a day and look at appropriate places to stop for the night. I used to use those AAA triptiks, but they probably have some fancy digital version by this point.
You could also just get in the car and go. I've done that on more than one occasion and it usually works out just fine. I really like road trips though, so more planning might be useful for someone who isn't me. You might want to get your oil changed if it's due and also just have someone do a once-over on your car to make sure you won't encounter any troubles.