I'd add the city of Los Alamos and Bradbury Science Museum.
The High Road to Taos (from Sante Fe) and Taos Pueblo
I love Sante Fe and highly recommend walking around the Plaza, going to all the museums, and having lunch at The Shed. Their posole is great. We like the Trailer Ranch campground (age 55+) in town on the bus line.
I'm also a fan of Georgia O'Keeffe, so besides the museum in Sante Fe, I'd recommend going up to Abiquiu where she lived and worked. With prior reservation, you can tour her house. Then go to nearby Ghost Ranch where she also lived and take one of their tours in the afternoon (book ahead.) Have a green chile cheeseburger at Bode's general store and gas station for lunch, and spend the night (or longer) at the Army COE Riana campground overlooking Abiquiu Lake.