Okay, I may be going on a limb here by choosing something not in the location, but things might work out.

Location
Milwaukee, Wisconsin. Specifically, the Eastside of the city.

Month
Late June - Early July

Days
June 30th to July 10th.

Activities
I can't hold to myself the joy of Summerfest any longer. Summerfest is an 11-day festival of music, games, and culture. I'd almost guarentee that there is something for everyone at Summerfest, may it be a trinket shop or a major artist playing at the Marcus. For example, Last year in one say I saw Dropbox, Motion City Soundtrack, Dark Star Orchestra, and Lewis Black. Rock, Emo, Prog, and Comedy. I'm sure that I just appealed to maybe half the community with that statement there.

Funds
Once again, depends on the day that we go. Usually they have freebies if you have certain items, but if we go between 10AM-Noon on Children's Fest, admission to the ENTIRE PARK is absolutely free. And if people want to see the band(s) at the Marcus, They give out wristbands to people that show up before Noon, or before they run out of bands, whichever comes first.
So, all you'd really need is money for food and shopping. Bring what you want, but I reccomend at least 20$ for lunch and dinner.

See? A very efficent, entertaining, and wallet-friendly idea. And Milwaukee is just 2 hours away from Chicago, so it's not that big of a jump from the origional suggestion of IL in the "Where" category.