Both Yosemite and Death Valley offer a number of choices for mobility-impaired visitors. As others have noted, Yosemite's main valley area is flat. Not only are there tons of amazing sights that can be seen from the side of the road but there are also many paved, level trails. Death Valley has several short, level trails too. Some are paved, others are not paved but are smooth. For example, the short trail out to Badwater Basin, elev 282' below sea level, is covered with crushed gypsum. A person with a cane can make it.
Weather is another issue you should consider for your trip. Yosemite in November is hit-or-miss. It might be snowing or icy, which can seriously complicate travel. Even if the weather isn't a problem, November is about the worst time of year for seeing Yosemite's iconic waterfalls. Some will be have very diminished flow, others will be completely dry. By contrast, November is a good time to visit Death Valley. The temperatures are usually comfortable, not deadly hot like in the summer or disappointingly cool like in the winter.