So, should charities remind people that donating will make them happy?

I worry that this might actually have the opposite effect.

There was a time when I helped people due to an explicit goal to feel good about myself, and less because I cared about them. Over time, it changed to me helping them because I wanted to. But before it did, I actually got very little satisfaction out of helping them, because I knew I was just doing it for selfish reasons. I remember complaining about this to someone.