I am now in Chicago and within charming range within all relatives.

This is how things are shaping up:

Free rooms:
1st option) We have access to two living-office condos and a third living condo for free. These are close to the city, and the two offices have great views that'll make you forget about how cramped it is. Plus, there's a pool.
But:
-We're short on beds and quite a few people may end up sharing air matresses, or sheeted couches (they're really comfy).
-Food in the city is expensive.
-There are (on average) two toilets, one shower, one bath tub per condo. There's bathrooms downstairs, but shower tickets may need to be used.
-On weekdays, the residents of the upper office must evacuate before 9AM (preferably 8AM ;|), and leave no evidence!

2nd option) My mother has a two story house that's too big for the family. And none of the family lives in it either. We could probably lay out air-matresses all around, utilize the basement + 1st floor + 2nd floor, and buy non-perishable food for meals at sub-urb prices. It's her house, so there aren't as many rules. The walk to the train station is about 15 minutes, and week passes aren't horribly expensive. The pedestrians get the best out of Chicago's travel system.

3rd option) All of the above. If everybody brought their own sleeping tools, there's enough shelter for all interested. This comes with segmented groups though, and I'll hate each and every one of you as I switch between shelters to maintain order.

Date: I'm up for anything in the months June, July, August inclusive. The living condo is not available during July-4th week.
There are two main highlighted weeks that I can name off the top of my head.
July-4th
Fireworks.
Taste of Chicago (expensive, but exotic).
Taking the third living option without the first one so much.

August 1-3
Tradition.
If there's less than 18 people, we can all fit downtown.
Lollapalooza (You're paying for your own tickets >(.)

Other than that, any week is fine since CHICAGO is a great place; we'll have plenty to do. There are interesting museums, great restaurants, sightseeing, parks, Navy Pier, shopping malls, etc.

Things yet to be:
Definitive schedule of events (submit your ideals).
Headcount.
Maps to aid traveling to the living places.
Things yet to be list.

I am only in Chicago until the New Year, and then I'm back in school.
POST YOUR QUESTIONS NOW.

Current quesitons:
"If we had to estimate on how much it would cost there for groceries, possible other hotel room, games, attraction, and possible eating out... about how much do you estimate will be the cost?"

Great question! Give me a week to scour the city and it's attactions ;X.

"Are there hotel options nearby that we could mix in as well?"

Not without more segmentation. There's few (cheap) hotels around the condo-section of town. I will ask around though (and greet any attempts to find hotels).

What airport would we be flying into?
Chicago O'Hare (ORD) or
Chicago Midway (MDW) work equally well.
I know O'Hare better than Midway, but both of them have a train-station that links them to Chicago down-town. At $2, it's money well spent to lug baggage to downtown.