I'm an artist who plans to start a website where I will donate partial proceeds of the sales of my work to various charities on a permanent basis. What is the best system is to do this? Should the partial proceeds be transferred to each charity on a weekly, monthly or quarterly basis? Will the relationship be different with each charity? Also, how can I be transparent to my customers? Will they request proof of their donation and, if so, how do I go about doing this? Will the donation be a tax write-off for the customer, or for my business?