One of the highlights of our vacation last year was finding the back gate of Area 51. My 12YO son can't stop talking about it.
A must place to stop at is the Little Ale'in Inn in Rachel. Great chili!
There's a nature preserve about an hour south, can't remember the name. I found it fascinating, an oasis in the middle of the desert.
I really enjoy driving from Dallas to Reno: Route 66/I40, Southern Utah/Northern AZ, just so much to see and do.