I hope that your message is somehow seen by Lisa Fong. A year ago, a very kind lady, Virginia Quin Kay, with whom I had the honor and great pleasure of communicating, passed away suddenly. She had told me a couple of stories regarding Benson Fong, and how her son used to hang around Mr. Fong's Hollywood restaurant, Ah Fong. I have a feeling that she might have been able to connect you with Benson Fong's daughter, but, alas...
I hope to meet with some of Keye Luke's family members in less than a month from now at a showing of a Charlie Chan film. If you like, I will see if any of them have ever had any contact with Benson Fong or his family.