I worked at the zoo when they were designing that area. My family used to have BDay parties there for the kids in the family.
How about Lake Chabot? There are areas there we could use for a chicken stock and lots of parking.
San Leandro Marina, ohoh oh Garin Park in Hayward. By the old barn, Coyote park. Lots of places. The Marina is maybe a good choice since it has the space and is also near so much. My favorite park on this side of the Bay though has always been Tildon. Montclair has a nice park too. Lake Temescal....so many places. Joaquin Miller.....oh wait......that's the makeout park.
I knew people in hayward that work for HARD and could find out what parks in Hayward could be used.