Dear Felix
I am honored that you would like us to sponsor your charity. Indeed, it will be our pleasure to associate our name with your fine cause.
{Enclosed, please find a check in the amount of $[AMOUNT] payable to [CHARITY]. Please forward a tax receipt to me at your earliest convenience.}
Call me at XXX-XX-XX to discuss how we can go forward with the sponsorship.
Regards
Lydia