probably already been discussed but chicago pro tips for dlew, ronpricesgoatee, doom_catz and myself? going for fourth of july.
Oh man, you guys are going to have an awesome time! I lived in Chicago (suburb of anyway) for nine years and my wife and I went there every summer before having kids.
You'll want to watch the fireworks at the Navy Pier. It's absolutely the place to be. Bars, beer vendors, lots and lots of people.
Places to eat: Popular pizza places are Lou Malnati's, Geno's East, Giordano's all for deep dish and for thin my favorite place is Aurelio's. For a chicago style hot dog, try Hot Dougs or Portillos. For Italian Beef sandwich, either Al's Beef or Mr. Beef.
For fine dining, ask Clams, he's probably heard of some places. We were poor when we used to go visit so never went anywhere really nice.
As far as places to stay, anywhere in the Loop is good.
Bars: Clubbing really isn't my thing anymore but if you're visiting Chicago you have to go to a place called The Castle, formerly known as Excalibur. It has multiple bars each with it's own theme in this giant building downtown. Also for a fantastic outdoor pak'n experience there is the ROOF on theWit. 7000 square foot rooftop bar. FYI, drinks are very expensive, like New York expensive so pre-party as necessary.
Whoever said don't bring a girlfriend was right. If you play your cards right, it shouldn't be too hard to find a different girlfriend each night.