When we moved out to AZ, we drove from Albany, NY to Phoenix in five days, pulling a utility trailer. Once we got down to NC, we got on I-40 and took it all the way to Flagstaff. I assume that is the route you will take, and hey, it is a breeze. Just keep a-going.
I strongly advise a GPS. Not only does it tell you where you are, when to turn and where, but it will tell you exactly how far the next rest area is, what exit to get gas, food or motels, highway construction, and other really helpful stuff.
We didn’t have it on the way out, but did get the AAA Triptik. If you belong, these are really helpful, as they give all of the above info in a little, multi-page folder. Study it before and at every stop.
I also agree about stopping every 2-3 hours to walk around the car, stretch, and get the circulation going. I assume you have cruise control, so set it at 5 mph over the limit and rest your legs. Actually, in most places you will be OK at 9 mph over.
Thw walkie-talkies are also a very good idea, as there may be some places you can’t get cell phone reception, and besides, you will run up a huge phone bill if you are talking all the time. The walkie-talkies are not that expensive, and can really be helpful in an emergency. Like suddenly having to take a potty break at the next rest area. 
I used to have both a CD radio and a fuzz-buster, and it was like having diplomatic immunity.