The auction idea is great, but think about something. If there are multiple people willing to pay, say, $1,700, $1,600, $1,500, and many more with lower amounts - to meet Ashley Brookes, for example - why can't she just see more than 1 person?
Each one of those people was willing to donate that amount, so what's the difference if they ALL meet her and this way donate 10 times the amount a single winner would donate?