I also did it once as a kid (well, junior in high school). A neighbor friend of my mom's was a surgeon and lent us scrubs, head covering and mask. I seem to recall raising about $50, which to me was a very large amount of money at the time.
My mom wanted to go the day before Halloween so I could chaperone my sister on halloween itself, and a couple of people groused about it not being Halloween, but they contributed anyway ...