Top of the Mark, 999 California St; Nob Hill; 415.616.6916
Because you're pretty sure their generation invented it, take them for a Happy Hour at this super-high-up spot with amazing views of the entire Bay (or fog layer, depending), where you can grab stiff drinks, hear some stories about the Korean War, and re-learn that your sweet little grandma could drink you under the table if she wanted.
Palace of Fine Arts, 3301 Lyon St; The Presidio; 415.563.6504
Just take a (slow) walk around this historic building before going in for whatever cool event you bought tickets for (the Broadway exposition over Russell Brand?) right before your grandpa makes the most of your spent money by falling asleep.
THE GUEST: YOUR FRAT BUDDY WHO CAN'T DRINK ANYMORE FOR VARIOUS REASONS
After one too many times waking up pantsless in an area he's not quite familiar with, Ol' Kimball is on the sober-only fun path, and since he's your brother-in-frat-arms, it's your duty to get into as much mischief that doesn't actually involve mischief, like, say, five still-fun-with-no-booze spots:
House of Air, 926 Mason St; The Presidio; 415.345.9675
Take him and a group of buddies to this trampoline spot for some serious fun with dodgeball, the giant trampoline stadium, and a brutal reminder that your Bro Nameth's sobriety has left him in much better shape than you.