Hi R. -
First, I second the opinion of Gino's East. They have the BEST deep dish pizza!
Secondly, you can find so much to do along the "Magnificent Mile". There are plenty of shops at Navy Pier and lots of museums and the like.
Third, if you really want to enjoy yourself, I suggest you bring extra spending cash. I wish I would have known about Mamasource when my hubby and I honeymooned in Chicago for a weekend, because I would have been on asking the same question you are now. We were shocked at the prices of most things there! The parking lot prices are ridiculous (we found some asking upwards of $20, I'm not kidding), gas was more expensive, entertainment was pricey, and I could go on and on...Stuff you can't find out by viewing the City of Chicago's visitor website.
Fourth, if you're driving, STOP AND PAY EVERY TOLL YOU SEE, unless you have one of those i-passes. When my husband and I went on 2007, we didn't know we were supposed to stop at each and every single toll booth, which is apparently what you're supposed to do. Well, this past January we got a nice little bill from the State of Illinois transit authority to the tune of almost $300!!!!! We passed four booths along our way thinking we were only supposed to stop at the booth that's on the exit you take from the freeway when you're ready to exit (I hope that made sense). Nope - according to the transit authority, you're supposed to get off at EACH EXIT, pay the toll, and get back on, unless you have an i-pass, which is a prepaid card that automatically deducts the toll fee each time you pass the toll booth. This of course wasn't clearly labeled and I refused to pay the bill, so they threatened to have my driver's license and registration suspended. The fee for missing each toll is the cost of the toll (80 cents), plus a late fee ($25), plus a missed toll fee ($50).
And finally, fifth, if you and your husband can tolerate sarcastic humor, try dining at Ed Debevic's. The food is mediocre, but the staff razzes everyone, which makes for an entertaining time!
I hope this helps you.