How do you write a polite letter declining to attend and donate to a charity event?

My boss (Exec VP) was sent a letter by the adult son of a business acquaintance, requesting that he sponsor a table ($1,000 and up) or donate an auction item for an event supporting an organization that this man personally belongs to. While he donates to many organizations he feels strongly towards, he does not wish to make a donation to this organization or attend this function. I need to write a letter declining. Any ideas on how to politely and respectfully decline to donate in this situation???