Golden Gate Park Kids
Golden Gate Park Playground
Kezar Dr., Golden Gate Park
The Koret's Children Quarter is one of the city's oldest (it was established at the end of the 19th-century, though refurbished many times in the intervening years), and it's also one of the most compelling, thanks to a hand-carved carousel, proximity to the California Academy of Sciences, rope-climbing walls, a huge concrete slide, and all kinds of play structures.
California Academy of Sciences
55 Music Concourse Dr., Golden Gate Park
This is an incredibly rich and well-staffed resource for everything science-related, from informative exhibits on the future of our planet, to an incredible planetarium, to a scaled-down rainforest complete with all sorts of live critters. On Thursday nights, they do a really fun adults-only party with numerous bars and amazing guest DJs.