Should I make a donation instead of giving a wedding gift?

I suppose you could go your own way with a gift. But if that is what they want, then why not? It seems like a selfless request from the couple.
But I thought you said on your previous question that they were registered at Tiffany’s.

I say why not also unless you are morally opposed to the group they are asking you to support.

Adopt a dog.

when I got married we asked for donations to be made on our behalf to the MS Society. Since I have MS the cause is very near & dear to our hearts. We could think of nothing more loving to celebrate our marriage as a gift. So, like Marina said, unless you are morally opposed to the charity they selected, then I would. If you are opposed to the charity, then I would pick another on that is representative of them.