I'm going to ICAAC myself - 95% of the attendees will be staying at one of the downtown conference hotels, not the Hyatt at McCormick just because of capacity issues (listed here -
http://www.icaac.org/index.php/registra ... nformation)
ICAAC is running shuttles from McCormick to the conference hotels - the easiest way to handle logistics for any event is to be able to tell your cocktail guests to get on a specific shuttle & then get off at one of the hotel stops near your cocktails location.
For example, take shuttle 3, get off at the Embassy Suites stop on State Street & then cross the road to Quartino. They have a private room & would be an okay option, though there are others.
The Gage would not be a good option since none of the shuttle stops are anywhere close & you'll have problems getting people there.
Since shuttle 3 serves the greatest number of hotels & will be close to people's dinner appointments I'd suggest looking for options near these hotels.
Westin Chicago River North On Dearborn at Kinzie
Courtyard Chicago Downtown River North On Dearborn at Hubbard
Embassy Suites Downtown Chicago Curbside on State
Chicago Marriott Magnificent Mile On Ohio at Rush
Four Points Sheraton Downtown On Ohio at Rush