Good on you Mom!! Western suggestions: In AZ on I 40 turn north on Us 191 (exit 333 (Chambers) and follow it to Chinle ( Canyon de Chelly. Good cg there for you. En rote to Chinle stop for an hour or so at the Hubble Trading Post (near Ganado. At the Canyon do take the Navajo-guide tour of the Canyon.
Then back on 191 go north into Utah to near Bluff and take US 163 south down thru' Monument Valley. Again a Navajo-guided tour is as must (IMHO).
Back on 193 south to 160 and west to 89, south to Flagstaff (I 40) and west to Williams. Then north for Grand Canyon. back o to Williams and west on I 40 to Kingman then 93 to Hoover Dam and into NV and Vegas.
Your choice for CA is there - I15 into LA area or north to Reno and US 50 over to Sacramento/ SF areas. then north.
Be sure to keep us informed about your 'epic' journey!
John