Seek 'n Spell in Golden Gate Park
Details
Pioneer East Meadow is a large basin-y meadow on the south (left) side of JFK Drive before you get to Stow Lake Drive (when you're heading towards the ocean). JFK Dr. is closed to cars on that stretch during the weekends, so if you're driving, the best way to get there is via MLK Jr. Dr. to Stow Lake Dr. and park as close to the boathouse/bathrooms as you can.
No need to bring anything other than an iPhone/Android and your smiling face, and maybe a jacket depending on the weather. Don't worry if you don't have a smartphone, we'll have extras so everyone can join in the fun. Hope to see you there!