I know that you are only playing devil's advocate pearlieq, but I feel like I have to speak to this since we are giving a charitable donation. Please don't take this as an insult to you. Instead I am directing it to the people who would have a problem with my choice of party favour.
If people are offended by our choice of charity, to put it bluntly, too bad. I can't imagine any body being offended by us wanted to support a starving people (for example) rather than getting a chocolate truffle or something. A wedding is supposed to represent the couple and this gesture very much represents us. We give private donations weekly. I am going to technically work for a charity for the rest of my life. As far as charitable donations being self-serving -

. There are many organizations that depend on people being self-serving, then. I guess you could say that it's self-serving to buy fancy, expensive favours. The couple could be seen as wanting to impress the guests. Honestly, if someone has a problem with this, they can go pound sand.
Ali