Hesperian is a perfect not too popular park equipped with a play structure for a kid ready to climb! 

This gated park is right next to Hesperian Elementary and has three entry points (two on Mills Ave and one on Drew St). With a nice sidewalk connecting the two, an open grassy area along the path and a big shade tree, this is a perfect park for a picnic!

The playground has a swing set (with standard and bucket swings) and three spring riders! The structure has three slides (a spiral and the other is side by side), two ladders, steps, a bridge, a balance beam, and those climbing walls you see with the holes, not rocks. A feature the climbers in your life will really enjoy is the angled step bars that ascend to meet a pole that connects and allows for maneuvering to do the descending version. This climbing bridge really confirmed to me that if you let your kids try new adventures or skills their confidence and agility will skyrocket. 

When we went there was a big hole near the fence where a tree has been removed so watch out for that. The park was empty when we got there but maybe five families when we left. There are no bathrooms and no parking lot (but easy street parking).
This park really is a hidden gem of San Lorenzo. Many people have never heard of it and because it is tucked away in a neighborhood, it is not heavily visited.