At a Nightclub, Whereabouts Unknown

Left to right: Gene and Marion (friends of my parents, last name unknown); an unknown woman;
my mother (Elva Crabtree Harris); her younger brother, David Crabtree; and my father, Daniel Harris

This picture is a hard one for me to puzzle out. I know that my parents knew Gene and Marion in San Francisco, and visited them in Pennsylvania some years after this photo. I was born before we moved to San Francisco from Maine, but the only babysitter I remember was my Uncle David, who is in the photo. Was the photo taken before I was born, and thus in Maine? Or was it taken when we first lived in San Francisco? Who was taking care of me?