Here's an easy tour to take a guest with, one who visits in the summer. I did this today with a college friend. But we had to leave very early on a Sunday, and got back home for dinner.
800am - Take metra train to Ogilvie. Have breakfast at the food court while waiting for the first water taxi going to Michigan Ave
9:45am - Take water taxi ($5) from Ogilvie/River North going to Michigan Ave. Purchase Architecture Boat Tour tickets ($35) at Wendella, where the water taxi docks at. The first architecture tour is at 10:30am. Will be done right before noon, still a little full from breakfast, so can manage to walk up north to John Hancock Tower.
Spend an hour at the John Hancock Tower, $20 general admission.
Around 1pm, walk 2 blocks south to Gino's East for Chicago Deep Dish Pizza. It will take 45 minutes to make the pizza so it pays off to have your guest eat a heavy breakfast earlier at the Ogilvie.
3pm - Walk all the way south to the Millenium Park for the Cloud Gate, the Crown Fountain, the Garden, and the Pavillion.
Walk a block south to the Art Institute of Chicago then walk along Adams Street going west. In a 2 blocks, stop by CVS for cheaper souvenir T-Shirts ($5 each). Continue to walk till Wacker, take a quick photo at the main entrance of the Willis Tower. When back up north west to Ogilvie for the 6:35pm train home.