Apparently there's a rule against referring to wedding gifts that's so hard and fast that you're not even supposed to mention them long enough to say you don't want any, or that if you really insist you should donate to these charities.
Well, I think that's bollocks. We've got our 20th anniversary and vow renewal coming up in a bit more than a year, and we want to direct people to a few select charities (probably The Nature Conservancy, Doctors Without Borders, and The Vermont Foodbank) if they feel a need to do something. (Which we wouldn't expect as a vow renewal isn't precisely a wedding, but some people will anyway.) In any case, we don't want gifts.
It's a polite but supremely ridiculous fiction that wedding gifts are supposed to be unexpected and wholly a surprise. (And if it's not absurd enough, there's a whole industry built around wedding registries!) Carrying on such absurd fictions to conform with the social contract is fine when it doesn't hurt anyone. But if, because we feel a need to conform with it, someone doesn't make a donation and so someone goes hungry, that's ridiculous.
Social contracts only change because someone changes them. If people think we're being inexcusably crass for saying "No gifts wanted", or for pointing people to selected charities, then to heck with them.