Your trip is taking shape and looks pretty good. I am wondering why you're skipping driving on the coast in California? CA-1 is a bit more tiring for the driver, especially when driving an RV, with its twists on a relatively narrow road. Yet the views are amazing. You might consider, at the very least, doing this stretch along CA-1 if you don't feel you can do the whole SF-LA leg along the coast. This way you don't have to do that little run out to the coast for Hearst Castle and then backtrack to get back to 101. The views are really worth it.

Amarillo (some old cars buried in sand)
That would be Cadillac Ranch.

Santa Fe (we would like to see some indian reservates, isn't it near by?)
Here's a good map of Native American reservations in New Mexico. Download the PDF to enlarge it. I'm wondering if you're thinking about Taos and the Taos Pueblo? Taos is about 2 hours north of Santa Fe.

Santa Fe is also a very cool city with lots of architecture, museums, history and some Native American stuff as well.

If you find that these are too much of a detour, you might enjoy Albuquerque, also a beautiful city. You will get a taste of Native American culture there.

I'm not real familiar with where the best Native American places to visit are along your route, nor which will be the easiest to visit. Hopefully these will give you some ideas and someone else with more knowledge will pop in here.