I'd leave it open for a while. At least wait until some time passes between donation. You were going to close it a few days ago, and somebody gave £500 today, so it may be that some people are just finding out about it.

I'd also ignore the critics. You can choose to focus on their belief that Dick doesn't deserve it, or you can know in your heart that you're doing a good thing, focus on that, and let the rest go.