Donation drive instead of gifts?

If you don't register, that will give your guests the hint that you don't want gifts so they'll give you cash/checks instead. Personally, I would just accept the money and use them to donate however you please. I think your ideas are nice, but I don't see folks bringing toys or jackets to a wedding for a donation box. I also wouldn't directly ask for donations, just because it still comes across as asking people for money. At the most, I might put a box out on your wedding day that says "charity fund" with maybe a little notecard explaining what the money will be used for. This should keep your guests from feeling obligated.

Wow good for you. I think this is a great idea. If you simply don't register then people will assume you want cash. To avoid that as well you could say something like: "Although your presence is gift enough, if you are inclined to gift us for our wedding we would appreciate donations of (toys, jackets, whatever it is) in lieu of gifts for us. We will donate these items to the ___ charity following the wedding". Something like that! Maybe someone below will be better with wordsmithing this one.

I agree with this. Then you can just donate the cash! I've seen links on wedding websites where you can donate to a charity in the couples name too.

I think your intentions are very good but involving charities with weddings sometimes gets awkward for guests. Hypothetically, they might not approve of the charity you choose, they might feel obligated to give you a gift AND bring a donation, or they might stress about how much to give if they haven't seen a charitable appeal combined with a wedding before. There are several possible unintended consequences.

I think it's much simpler and "cleaner" to just not register and to spread the word that you don't need anything. Make sure to tell your parents your wishes, so they can help spread the word. If anyone asks you directly, thank them and say you have everything you need and will just appreciate their presence at the wedding. Some people will still give you gifts out of habit. Definitely feel free to donate all cash gifts to the charity of your choice as that is always appropriate.