The bus around town is another good idea... cabs can be a bit of a pain (and expensive) and walking is not really practical to all the sites (such as if you parked close to michigan ave and wanted to see the field, shear aquarium or planaterium. the aquarium and planaterium are really close together but the field is out on its own) Navy pier is fun, a bit of shopping and the farriswheel is great. They even have a boat tour that takes you out onto the lake. Its a wee bit pricey about 24 bucks per person... but its seriously worth it, and it kills alotof time while they wait.

Word of advice if you are staying the night in the city. Be careful where you book your hotel, you want as close to the maginifican mile (michiagn street) as possible especially if you are staying on a sunday. My husband and I for our honey moon made the mistake of staying in a business district... so on sunday the street was dead except for fishy characters. Good luck and have fun. Chicago is a wonderful place to be!