Legal Question in Business Law in California

In my view, there is a big difference between "any mention" (which the charity probably couldn't prevent) and a statement that a portion of the proceeds from each sale goes to the charity, which I believe the charity can lawfully demand. The first is a First Amendment free-speech right. The latter is a potentially misleading suggestion that there is an agreement between the charity and you; it also places you in a position of appearing to be the charity's agent for the receipt of gifts, which you aren't. I don't know of any statute or case law on this topic, but I would not be at all surprised if there were.