There is so much for everybody to do and see at Yosemite. Once you are tired of seeing the hotspots, you can just stroll around at the marked vista points and experience the beauty of vast landscapes. Most of these spots have benches, offering you an opportunity to grab a meal.
We had to visit the Mirror Lake in the end before signing-off on Yosemite. But that too required walking a couple of miles to and fro on a paved path from shuttle stop #17. However, there is a beautiful stream to accompany you. After an exhaustive day, I found sitting there so therapeutic.
As regards the lake itself, it is a worthy attraction, offering stunning reflections of surrounding cliffs. The best time for views is spring and early summer because of snowmelt from Tenaya creek.
If you wish, you can loop around the lake too, which is about 5 miles round-trip and needs 2-3 hours at the minimum.
Yosemite is a once-in-a-lifetime experience. If you get to be nearby, do visit this amazing gift of nature!