
Greetings from Hoover, neighbor.
I have made the drive along I40 three times in the last 7 summers and have some suggestions.
First, stop at the Big Texan steakhouse for a big delicious, good value steak meal.
http://bigtexan.com/menu/ It's relatively affordable and fun to see someone trying to eat the 72oz steak meal for free in an hour. Seen 4 people try it across 2 of my visits, only 1 was successful. I've had the 24oz ribeye twice and the 36oz once and they were all good. It's cheesy Texas tourism but it's fun and delicious. It's on I40 in Amarillo, TX.
Second, if you are going as far as the Grand Canyon area, is to stop in Williams, AZ and ride the Grand Canyon Railroad to the National Park and back. Don't know if you are staying at the Park (I backpacked down to Phantom Ranch and back up to the South Rim in 2009 - great trip) but the train ride alone is worth doing.
http://www.thetrain.com/?gclid=CJvu34Tj58MCFRckgQodJDQAtA They also have an RV park across the street from the station in Williams if you are taking a camper with you. The GCRR was recently bought by Xanterra who runs the National Park's hotels and some maybe a campground on premise as well so they are trying to make the train a seamless experience with the Park.
Of course the GC, even if you weren't planning to stop, is something everyone should see even if it's literally just a look out over the edge. It's an hour's drive off the Interstate each way to the South Rim but it's worth it.
You'll see many of these in TX (not trucks, wind generators).
And oh it can get hot.
Sounds like a nice trip.
For campgrounds, we made it from Birmingham to Lake Eufala State Park in Oklahoma. It's not that great and showerhouses were cinderblock, small, not air conditioned. The KOA about 10-15 miles west is better. The town just before that, Checotah, has a Denny's now off the Interstate about a mile on Hwy 69 north and across the other side of 69 is a Wal-Mart. We camped other places off the I40 corridor before we got to Williams so I can't speak to any others.
Oh, and third in Albuquerque the tramway up Sandia Peak is interesting and a great view.
http://sandiapeak.com/index.php?page=sandia-peak-tramway
Bama Ed
PS - Also as you head west from Amarillo before the New Mexico border, the landscape changes dramatically. On the Amarillo side you are on the plains/prairie but then you feel yourself driving down hill and the scene becomes more dry scrub and desert-like. It's weird but cool.