Rehearsal Dinner, 50-75 guests
Scoozi and Hub 51 are both part of the Lettuce Entertain You empire, which covers a wide variety of price points, cuisines, etc. I've eaten at both, and they're both reasonably good, albeit not breaking any boundaries in creativity. LEY places are generally excellent at the ability to serve private parties (having everything come out at the same time, etc). With a large group, that can be more important than food that may be better when a group of 2-6 is eating.
For tips on arranging private parties, see this discussion:
Dinner and Drinks for 40? - www.chow.com/topics/799823
Here are walking distances (per Google Maps) from the Monaco to places that have been mentioned thus far:
Scoozi 1.2 miles
Hub 51 0.4 mile
Baume & Brix 0.8 mile
GT Fish & Oyster 0.8 mile
Portillo's 0.7 mile
Quartino 0.6 mile
You might also call the concierge at the Monaco for additional suggestions of places that are close by.
I was at a rehersal dinner at Portillo's that was super fun and they have the BEST chocolate cake. A chicago dog bar, chopped salads and beef sweet and wet -- what could be bad about that. They serve beer and wine too.
Oh yeah, and its cheap and totally old-school Chicago. About a 15 minutes walk from Monaco.
I love Baume & Brix as well as GT Fish & Oyster. I know both have space for private events, but I am not sure what size they hold or price point. They are both a little under a mile away from your hotel.