I lived in OKC (Harrah) for 8 years and drove back to CA 16 times on I40. After a few times, we started leaving after school was out (3-4pm) and driving as far as we could. (since you gain an hour in NM, we would make it to the first town in NM (Tucumcari I think)and spend the night at the Holiday Inn there-they have a free hot breakfast there). NM usually takes 6 hours to drive through and also AZ. In 10 hours driving we would be in Flaggstaff where we'd stay the next night. We drove up to the Grand Canyon from there. (Cracker Barrel is also there). We have pulled off in Winslow AZ to see the "Standing on a corner, Eagles song" which was different. The meteor crater we started to drive to see but it took forever on a side road and we still weren't there. I would rather keep driving to get me to the Grand Canyon. They have fake dinasours on the side of the road which use to keep my son busy for awhile (he's 20 now so that's not doing the trick any longer


).
I'm probably in the miniority but driving to the south rim of the Grand Canyon and spending 3 hours was good for us. We got an ice cream, ate at the cafe place. We weren't too interested in staying longer.
TX, there is a huge cross that you will not miss if that is something that interests you. People stop and look, pray. You will see all the signs for the 32 oz steak, we've never stopped to eat as it's just 3-1/2 hours from the house. On our first trips, we use to stop at the rest stops in NM to check out the red rock, bee hive rocks.
Watch how the landscape changes after you come down from the hills after Techapapi.
The Flying J and the other major truckstop (can't remember the name) were clean and had clean bathrooms. Have a great trip! We use to drive to Sacramento in 2 days but as we got older, the extra half day (after school and just driving 3-4 hours) was nice.