Lots of things to do in Chicago. Here are some of them.
Arrive at Ohare or Midway airports. Ride the CTA train into the city - it is cheap, convenient, and interesting. The train from O'Hare runs as a subway and as an elevated line, giving you a glimpse of the city. The train from Midway is elevated and goes around the Chicago Loop.
There are a wide variety of hotels in Chicago. Stay downtown if you can. There are cheaper alternatives in the suburbs.
Things to see that are in downtown
Millenium Park - millenniumpark.org
Art Institute artic.edu
Navy Pier navypier.com
Walk Michigan Ave "The Magnificent Mile" hemagnificentmile.com
Buckingham Fountain huffingtonpost.com/2013/05/02/buckingham-fountain-chica_n_3195884.html
Grant Park wikipedia.org/wiki/Grant_Park_(Chicago)
Architectural Tour architecture.org/tours
Field Museum fieldmuseum.org
Lake Shore Drive Lake Shore Drive
Lincoln Park chicagoparkdistrict.com/parks/lincoln-park
Lincoln Park Zoo lpzoo.org
A Little Further Out
Museum of Science and Industry msichicago.org
Chicago History chicagohistory.org