Outdoor activities for toddlers near Trestle Glen/Piedmont?

I'm looking for an outdoor weekday activity or two for our nanny to bring two toddlers (14 months and almost 2 yrs old) to, ideally near Trestle Glen or Piedmont though short drives are fine as well. We've found a great outdoor music class but are hoping to find another activity. In reading through previous posts I've primarily found recommendations for indoor activities or things a little too far away. Would love any recommendations--thanks!