A professional way of writing this...?

I have been with my job for several years now. I had training set up for July 2011, and had to cancel the training. My husband accepted a temporary job in July because we really need the money (and it is a high paying temporary job). I tried to find a babysitter for the 2 weeks I was going to be away, but couldn't find one. My job said that it was perfectly okay for me to reschedule, but that I had to provide a letter for supervisor to sign stating my reason for cancellation. I'm good at writing letters, but horrible with professional "explanation". Could someone please offer me advice on how to explain this without making my job and my training sound any less important in the letter. Any advice is appreciated! Thank you and have a good day. : )