How's this for cause-and-effect as a strategy? Give money to the Knights of Columbus, and this guy gets a wheelchair. It makes him so happy, he gives a "thumbs up." I'm sure there is a lot of good being done, but something about the visual and the headline made me laugh.
However . . . I think the call to action is effective, because it is specific. "Each $75 donation will deliver a wheelchair to a child, teen or adult without mobility." I've seen other charities use this approach, specifying a dollar amount and equating it with a direct result. Seems to me like a pretty strong tactic, since it's human nature to know where your money is going.