Well.... I feel for you. I just had 9 people contact me (in the beginning of January) asking about lessons. I turned them ALL down because I had no time slots. 4 weeks into January one of my mom's tells me that they have too much in their schedule so they need to take a break until next fall.
I had to be honest and told her because she hadn't given me 30 days notice I had to charge for the following month of lessons (February). I also explained how many people I turned down 3 weeks earlier - and now couldn't take any of them! She seemed to understand, but we'll see if she tries to return in the fall. I plan to be "full" if she does call.
.... and during the little girl's lesson - she blurts out how her and her sister are starting basketball the following week. Made me realize that piano was the easiest thing to ditch.

I found it no loss to lose them.