Velma Heist Warren wrote on this: "Pirson, Fries, Heist, Geyer, Flood, Bleyle cousins." Since most of these folks were from the Pirson side of the family, it may be that Velma's family were the only Heists.
Velma is lower left. Perhaps that is her dog Spot. Velma's mother Florence is just behind the person labeled Mae. Velma's father Howard Heist is second from the right in the back row. The man in the black suit may be Chris Flood.