We live about 2 minutes from this park and we hit nearly every other day. There are two sides to the park and huge historic home in the center, which has a couple small random businesses in it and I believe can still be rented. I totally went down a wikipedia rabbit hole on the Robson Harrington family and the house, it's pretty epic. Lumber baron, then sells to the Robsons, some other form or baron or industry and built these insane Roman gardens and threw epic parties (maybe Gatsby-esque?).
Anyway, I digress. The lower side is great for the dogs and has a bunch of picnic tables, great for kids birthdays or bring lunch over form nearby downtown San Anselmo. There's also the ruins of the gardens you can explore through. Most of the time, dogs are off-leash, including mine so if yours is unfriendly, sorry I'm not sorry, this spot is a local treasure and we don't take kindly to...kidding, but seriously just leave Fido on the leash, there's plenty of space. There's also two, always filled poop bag dispenser stations, so please pick up after Fido, you have no excuse.
We also take our daughter here, but we prefer the upper/front yard part of the house for her. It's generally quieter, less dogs, and it's flat. There's some more picnic tables, two mulberry trees (yes you can eat the fruit when it's dark purple) and a little tree grove with various places to sit. The grass can be a bit unruly but generally this place is kept up quite well - oh and there is exstensive community gardens, but I have NO idea how you get a little plot or who grows there but there is always someone there. read more