Death Valley?
Death Valley could be boring even for 80 year olds. What about something by the sea? The ocean cities are a tad warmer than inland. Off the top of my head, for a nice visit in southern California, Dana Point is lovely. Laguna Niguel has nice hotels, and you can find plenty of condos to rent near or on the beach. I used to live in San Diego, but I really am not that in tune to travel type places there. Dana Point has a lot of beautiful sailboats that older people (younger people too) might find interesting. The area is very picturesque and not as hurried as some parts of LA or San Diego.
just my two cents