I've taken clients to
One North Kitchen in the past, and thought it went over well with everyone. It's definitely got a "lunch meeting-friendly" atmosphere, and more-than-decent food. Prices are a touch steep, ~$40 per person for an app & an entree each, assuming no booze (gotta love the nonsensical American taboo re. having a glass of wine with a nice lunch). Interestingly, it looks like One North Kitchen is owned by Restaurants-America, the same folks who own Bar Louie.
I've also taken clients to, & had team lunches (where my spending limit is a bit lower) at,
Lloyd's Chicago. Some good seafood dishes, and lower prices than One North Kitchen, ~$25pp for an app & entree each. Both the atmosphere & the food is slightly less "upscale" than One North Kitchen, but it's still totally fitting for entertaining clients (or bosses) and talking business over lunch.
One North Kitchen & Bar
1 N. Wacker
(312) 750-9700
(northeast corner of Wacker & Madison, 5 minutes' walk from Franklin & Monroe)
Lloyd's Chicago
1 S. Wacker
312-407-6900
(southeast corner of Wacker & Madison, also 5 minutes' walk from your office)