Lesson Learned:
If you see a venue you like in Chicago and it's available for the date you want, put a hold on it. Some places (like Cafe Brauer) will let you hold for a week. Others, like the Chicago History Museum, will let you hold onto it, but if another couple wants your date, they can go to contract on it. You'll get first right of refusal, but then have to make your decision maybe more quickly than you would like.
I'm disappointed. I had already started imagining how we would set the rooms up, and I think too that because I know I can't have it, I artificially want it even more. Oh well. Tomorrow AF and I are going back to our other top choices to see if our dates are available (knock on wood!), and hopefully I will be able to post some better news.