Many classes are holding picnics as part of their reunion weekend. Most hold a dinner/dance event Saturday night, followed by a picnic the following day. Picnics area a great opportunity for people to drag (oops, bring) their kids along, plus there are those among us who prefer an outdoor gathering to an indoor one.
The most popular location seems to be Tilden Park. Tilden has picnic areas that can hold up to a couple hundred people (they say 150, but classes have squeezed in a few more), with huge BBQ pits and many picnic tables. The most popular seems to be Padre: Padre can hold 150 people, has ten large picnic tables, one huge BBQ grill, two food serving/prep tables, bathrooms with running water, and a large grass field (one of the few that is still watered). See the Yelp review of Padre here.Information about Tilden reservations can be found here. Some classes just say “Meet at the grass in front of Lake Anza” and have gatherings without reservations; this has worked as well, reservations are recommended if your reunion is on a popular holiday or summer weekend.
The City of Berkeley also has many parks that can be reserved.
Most groups make this a free event, with the minimal costs funded by the sales of tickets to the Saturday night dinner/dance.
It seems that pot-lucks are the menu-du-jour. It helps if organizers bring some ice with coolers, BBQ coals/spatulas and utensils/cups/paper plates. This keeps the cost down. You probably want to remind people coming from afar that they can come without a dish, since pot lucks usually have more than enough food.