How would you word this?

[JennJubie]

As I stated in another thread, I'm a go with my gut kind of person. So here's my problem: I had an interview booked with a family. Mom called me 20 minutes after they were supposed to be there and said "Oh, I completely forgot we had an appointment with you until now, can we reschedule?" and because I thought maybe just maybe it was an honest mistake I said ok. On the rescheduled day, they showed up 30 minutes late for the interview. During the interview Mom tells me that they are looking for full time Mon - Fri 8 - 4:30. Now she contacts me almost 3 weeks after our interview saying that she now wants only part time for an undetermined amount of time as her husband is still looking for work. I do NOT want to take on this family. My gut says NO NO NO. Any advice on a very polite way to tell them I won't take them on?