M.L.
You will pass through desert so make sure your car has a good tune up and that your tire tread is good before the trip. Carry plenty of water in case of a breakdown. For entertainment bring sing along music, books on tape and plenty of imagination! And also maybe look at the landmarks you will be driving past. You can tell the kids about the ones you might not have time to see. And give them a little history lesson as you go! I drove cross country with my parents many times growing up and it is fun (though sometimes stressful) time. Many good memories! Just remember to be a little flexible and stop when people need to. Plan some fun running around games for grassy rest areas and pic nic lunches instead of fast food when you can. Give them a break when they need it and it will be less stress on everyone. Many nice places to camp as you go if you are into that!