How to manage an interview you're not interested in?

Mentioned to a long-time family friend of mine that I was looking for new jobs and he said he would send my resume around to some people. I conveyed exactly what roles I was looking for to him and he set up an interview for a role I have never done and have no interest in. I feel bad that I owe it to him out of respect to do the call but frankly don't know anything about the job and feel it will be a huge waste of time for everyone involved. I know I should probably just come clean with the interviewer and say there has been a misunderstanding etc and cancel the call but am worried the family friend will get pissed I didn't atleast do it. What is everyone's thoughts on how to handle this? I've already had to reschedule the call from a firedrill at work twice.