Write a sponsorship letter for my thirteen year son.

My thirteen year son is looking for sponsors to help him achieve his dream of becoming a race car driver. I understand that the first, and most crucial step in this process is to write a letter that will touch the harts of the potential sponsers, and instill the desire to help us. For this to happen, I was told that we or the writer need to write a letter telling a story of how my son's desire to become a race car drive starteded. All this information will be provided once before the project is started.