I may be misremembering (and the situation is a bit different now, lending credence to the idea that I'm misremembering), but I think Bram Moolenaar used to req

I may be misremembering (and the situation is a bit different now, lending credence to the idea that I'm misremembering), but I think Bram Moolenaar used to request that people donate to the children of Uganda and send a post card to him. For people who would like that donation, I think that would be awesome: make the donation and send an email saying that you did it. This should provide the motivation you are looking for. Rather than a notification that money when into their bank account, it's a notification that it went into a bank account that they value higher.