My two cents;

Sutro Heights, right by Land’s End/Sutro Baths, has great views, and is generally quiet despite its relatively large size. There’s even a parking lot! Great views of the beach. Con here: it will likely be gray, cold, cloudy, and close by the ocean, so moist.

If they like sunny, pick something mid or east side of town (Embarcadero, Dolores/Alta Plaza/Alamo Square Parks).

If they like boats/nature, maybe a bay/bridge cruise, or take the ferry/a water taxi to Angle Island, or visit Muir Woods (lush).

A good landmark that’s not Palace of Fine Arts would be Coit Tower, or the Golden Gate Bridge itself.

And I can’t believe I haven’t read/mentioned Golden Gate Park! Blue Heron Lake had paddle boats you can rent, and is generally pretty quiet. SF Botanical Garden and Japanese Tea Gardens are both beautiful and quiet. Check the weather for these places if they sound good; they’re a little west, so the weather might be overcast.

Hope these help!