I just had to do the same thing. Mom was a control freak, argued with me over every aspect of my handbook and contract.

I just emailed them 2 days after the interview and told them I had chosen a family who I felt was a better fit for my program. Wished them luck in their search. End of story.

I've been 'biten' too many times so to speak. I love that I get to chose who comes into my program and not just have to take whoever wants to come!