My friend asked me to hire his under qualified son. How do I politely get out of the situation?

I manage a business and my oldest friend asked me to hire his son who is having trouble getting a summer job. The interview wasn’t that successful: the son is incredibly shy, doesn’t have any relevant work experience, doesn’t really seem to want to work, showed no interest in the business (didn’t ask me one question), and asked to not work on the weekends. How do I get out of this situation? When I walked into the office after the interview, one of my current staff said “some fresh meat?” meaning they will eat this kid alive. The lesser hurt will come in not hiring him, but what do I say to not destroy my friendship with his father?