M.M.
OK skip the Sears Tower if you come here. What a waste of time, so so overrated. A better view is Lakepoint Towers (restaurant at the top called Cite), best in the city. But if you have girls, you could have tea at the American Girl Store in the Water Tower and then go up to the 96th in the Hancock - right across the street - for a drink and a better view than Sears.
Here's what's up in town for that weekend:
9-10: Chicago Folk and Roots Festival
9-10: Gold Coast Art Fair (FREE)
9-10: Rock Around the Block
9-10: Roscoe Village Burger Fest
9-10: West Fest
9-10: Chicago Folk and Roots Festival
The Gold Coast art fair is fun, great walking, and close to the mag mile, if you choose to stay there. I go every year. You can also do the beach and the museums. Lots of kid friendly stuff.
I love Toronto, but you do need a passport to get there now - not sure if you have that. And Chicago would be a shorter ride, I'm guessing.