Looser bro, I am also a huge fan of road trips. Based on my expereince so far, I highly recommend you to use NATIONAL rental car company. They have their location on almost all the airports. National rental car is the parental company of Enterprise and Alamo. Here are reasons why you should use National. (I am in no way related to the company but have used it in the past ) 

- It's clear that you need a good size SUV for your trip. So, if you join the emerald club, all you need to do is book a midsize car and you can pick any cars, SUVs, Vans you like that are on the lot. Keep in mind, its free to join emrald club. 

- All the rental vehicles have very minimum mileage. Most of the time you will have a milage less than 5k. They wont use any vehicles more than 20k for emerald members.

- You get unlimited mileage and no cost for additional driver.

- Last but the not the least, check in and check out process are super easy and very fast. 

This is my sincere suggestion to a fellow country man and I am neither related nor interersted in this business but I am a happy customer of National. Good luck and have fun bro!!