Mark -
I lived in Chicago many years ago, and in the Fall of 2001 spent a couple of months on a special assignment in the Oak Brook area.
The first thought that comes to mind when I think Oak Brook is "velveetaland". I know that's not complementary - but the place is the epitome of suburbia - lots of mcmansions, lots of perfect green lawns, lots of strip malls with fast food restaurants, etc.
When I was there, I opted to stay in a less expensive Holiday Inn Express - not elegant, but convenient to where I needed to be. I was on expense account, but am naturally frugal, so I was able to find some reasonable places to eat. One of my favorites was a "mongolian barbecue" at the Oak Brook Mall; there is a branch of just about every fast food outlet and "family restaurant" chain on the planet somewhere along 22nd street.
Someone suggested going into town - I would agree with that. The Art Institue, the photography gallery at Columbia College, just walking around in the Loop, Central Photo (one of the worlds great camera stores - hasn't changed significantly in decades), the Near North and Old Town, the south side, University of Chicago, Museum of Science and Industry, the Field Museum of Natural History, Evanston and the Northwestern University campus, etc. Chicago is actually quite well known for its architecture (we all know about Frank Lloyd Wright, but his teacher, Louis Sullivan was a major influence on the city), and its neat just walking around looking at some of the older buildings. One architectural specialty in Chicago is churches - one could do a fascinating tour of the various architectural styles in the city's places of worship.
From Oak Brook, it will take you about an hour to drive into town - fortunately, the dominant traffic at 4:00pm will be outbound, so the drive won't be bad. Unfortunately, that won't leave you a lot of time to do much before things in town start closing down.