Have you seen Navy Pier since the renovation? It has changed for the better. You can take a high speed skyline tour out on Lake Michigan (it's fun!), or a leisurely architectural tour where they bring you down the river and explain all the buildings. Haven't done that one but I hear it's very good. (trivia note: a couple years ago, the bus driver from the Dave Matthew's band dumped the "potty" facilities of their bus over a bridge, and the poor folks taking the architectural tour got a little surprise. Bring an umbrella?
) Museum of Science and Industry and the Field museum are both very good if you haven't done that before. State Street & Miracle Mile are fun.
Good restaurants (Rick Bayless has a couple). It's been awhile since we've been downtown, but there are some good hotels and great restaurants.
When are you going? If you want I can do some backyard research. The papers are always full of things to do.
Last time I was there, they were completely renovating the Botanic Gardens. I don't know where they are in the renovation (I'm almost sure they are near completion), but it's beautiful either way.
Blue Man Group?
Do you want any Out-of-Chicago ideas? Will you have a car or be using public trans?
Our house? I'ts not exactly Hearst mansion.
Seriously, we're about 38 miles from the city so it would be a drive, but you're more than welcome. Free food!
Illinois Beach state park is beautiful, and there are some beautiful tumbled rock "souvenirs" that can be had by the bucketful.