I have what might be an unfeasible suggestion, but hey, why not...
Is it possible to cap the amount an individual is allowed to donate per donation? Still allow folks to donate as many times as they can manage to get in, but make them do it in whatever increment makes sense, whether it's $5 or $100. That would allow more folks to get in something, but would allow the people who are capable of donating larger amounts to still donate more if they choose, or if the target isn't reached otherwise. Am I making sense? Sometimes I do. 😛
I don't know if there's even a way to do that, but if so, I think it would make a lot of y'all happy.