Thank you for the witness vote! Upvoting is linked with a "post / comment" transaction - in order for the charity to receive an auto-upvote, it needs to post something, which is a bit of an artificial constraint. I was thinking about specifying a kind of Patreon for Steemit - but I need to study the former first. Basically an automatic system where someone buys steem, powers up and then directs a proportionate amount from the reward pool to the charity it wants to support at regular intervals, even if the charity has not "posted" anything meaningful to the blockchain (which could have been upvoted). I'll detail this in a post. Meanwhile, I suggest you get in contact with @shanibeer too (possibly on Discord)