Maybe contact some cancer association, and set up a auction during one of their events. Bigger is the association, more people will be there, and more money will be raised.
I did a similar thing for a local big association were a friend of mine belong. Every year they have a charity dinner auction, so I ask my friend what she though about one of my model (military diorama), that was connected on what the association represented. She was very excited about it, also because it was different than the other things they usually auctioned, but historically very important. Of course I was very happy, also after they told me how much money they raised with it.