Sounds like it'll be a great experience, Mike! Two or three classes of things come to mind for gift ideas.
First, as C2 suggested, local candy is a good idea,. There is some related Chicago history, also, to, er, sweeten your story, as this area was the original source for a number of American penny-candy-type treats. So you could bring representative Mars products as well as Ferrara Pan Candy's Lemonheads, colorful jawbreakers, and Red Hots. How about Frango Mints with their Marshall Field's large department store association? Not from Chicago, per se, but still uniquely North American, you might also consider maple-flavored candies--which ought to travel relatively lighter and more safely than maple syrup in bottles.
Second, I'd suggest packets of tea (or similar hot water drink additives) made with ginseng from Wisconsin. I'm told that the Wisconsin stuff is world-class (though to be diplomatic, one should say to the giftee that it might be
almost as good as ginseng local to Korea.

) You might try Ten Ren in Chinatown as a source.
Finally, on a less-healthful slant, I imagine that--as in China--there is considerable regard for packs of American cigarettes in gold packaging, e.g., Pall Mall.
Looking forward to a future posting of yours on your experiences, culinary and otherwise. Have a fabulous time, Mike!
--Matt
"If I have dined better than other men, it is because I stood on the shoulders of giants...and got the waiter's attention." --Sir Isaac "Ready to order NOW" Newton
"You worry too much. Eat some bacon... What? No, I got no idea if it'll make you feel better, I just made too much bacon." --Justin Halpern's dad