So far this is what I have learned:

There are cities of Oakley and Brentwood in Contra Costa County, California. This would be in Northern California.

The Native Sons and Native Daughters Adoption Agency could have been in San Rafael, Calif. (Northern Calif.) This agency handled adoptions of bi-racial children of Native American and White and ??? race combination. The idea being that these children would be adopted out to Native American families. This would point to the father being a Native American. The other possiblity would be that Mrs. Doering was a Native American. I am sure you realize that Doerings are basically German. I came across an adoption site that is for reuniting children with birth families. You might want to post there at Adoption.com. Posting there would give you an opportunity to connect to this group of folks. I would be sure to mention the name of the adoption agency. I went tot the site and saw that there are others who's adoption was handled by this same agency have posts as they are in search of birth families.