FYI, that is a great weekend to visit Chicago, the Air & Water show is that weekend. At least 2million people will head to the lakefront to view the show. I have seen it many times and it is still fun to watch and the the atmosphere is a blast. Also, the Cubs play at home against the Cardinals, Wrigley Field is an experience (big party) not a ballpark.
Air show review:
The skies over Chicagoland will come alive on August 20-21 with the sights and sounds of military and civilian aircraft... a spectacle rarely seen in a thriving metropolis. The Chicago Air & Water Show is the oldest and largest free admission show of its kind in the United States and will bring over 2 million spectators to the lakefront for the two-day event.
View fireworks from a Tall Ship:
Chicago's Fireworks - on a Tall Ship
Location: Chicago - Burnham Harbor
see the Navy Pier fireworks of the on a Tall Ship. The schooner Red Witch is just the ticket for a Wednesday or Saturday evening. The boat leaves at 7:30pm on Wednesday and 8:00 on Saturday. Reservations recommended but not required.
see a comedy show at Second City