No registry

I don't think it's proper to direct gift giving when it comes to gifts, even for charity and even if asked. A wedding isn't a fundraiser. A physical registry has the distinction of being arm's length. The spin is that it's a list of things the couple is collecting for themselves that guests have to search out in some way in order to find, for example on a store website, a plain link on a wedding website, or by word of mouth. In your situation, I would just continue to say that you are being honest when you say you are in need of nothing for the home. Either they will take you at face value, send a monetary gift or contribute to a charity of their own choice on their own time as they see fit.