One of the things I really like about living here in California is the parks: there are maybe four or five parks withing *walking* distance of our house, and tons within driving distance.
And they're all great: any one of them would be an exceptional park at home.
They all have tables and barbeque thingies (and you can bring your own), lots of green space, people walking dogs or playing volleyball, and (most importantly) swings and climbing frames and slides and whatnot.
One in particular near us (called Jack Fisher park) has a water play thingy: fountains and jets and the like. Great on a hot day.
Vasona park, not walkable but trivially driveable, has a big lake, and you can hire boats. (Or, I guess, bring your own.)