Here is a list of activities we enjoy doing with visitors:

-Lincoln Park Zoo
-Walk around Gold Coast and see the mansions
-Rent the Divvy bikes (on the Lyft app) and ride along lake shore trail
-Eat ice cream from Jenni’s
-Get a Chicago dog (Portillo’s is the classic place, but we really like Fatso’s last stand)
-Try deep dish (Giordano’s, Lou Malnati’s are the typical favorites but Ginos East is decent and Piquods is the local favorite)
-Visit millennium park to see the Bean and the splash pad - your 3 year old will love splashing in the water!
-Right next to that park is Buckingham Fountain, which is gorgeous! Grab a popsicle from a dude with a cooler and enjoy the beautiful skyline behind the fountain.
-Do the skywalk at the Willis Tower (formerly the Sears tower), it’s pricey but can be cool for kids
-Cubs game!
-Museum of Science and Industry is highly interactive and is a great place for kids!
-Fireworks at Navy Pier are free and can be seen from anywhere along the shoreline

Let me know if you need any more recommendations or if for any reason you find yourself in a bind, you got a cougar brother (and his HCBW) around.