The Hotel at Midtown is close to the venue, and there will be a shuttle for your convenience. But you can stay anywhere! Chicago has plenty of hotels all over the city in the Loop, River North, and Gold Coast neighborhoods. There will be complimentary valet parking at Rockwell on the River if you will be driving to the venue. If you're looking to do some shopping, head to the downtown area and walk down Michigan Avenue. There are lots of shops to choose from and great restaurants for some Chicago grub.
Per the card sent with the invitation, there will complimentary (FREE!) valet parking. This means that there is no cost to have your car parked by the valet service. (Usual tipping for valet services still applies, so please bring some cash for tipping purposes.)
No. You can wear other colors. "Black tie invited" means the event is formal and a tuxedo is preferred, but a dark suit is an acceptable alternative. Men should wear a dark suit with a white dress shirt and a tie (either a bow tie or a long tie), while women can wear a floor-length gown, a formal cocktail dress, or a dressy pantsuit. The key is to choose an outfit that is elegant and formal, respecting the level of sophistication set by the hosts who are likely dressed in black tie.