I Agree with Jaydrvr, get an EZ Pass or and I Pass (Illinois's version of EZ Pass) and breeze through the tolls. The I-Pass works all the way to the east coast fyi! Timing is everything in large cities and Chicago is no exception, 80-94 isn't too bad mid day. We've done it many many times! Coming from Indiana, you won't be on much of the toll road to begin with so paying online might work for you. If I remember correctly you have 7 days to go online and pay your tolls.
Stay in the middle lanes until you close in on the I-80 exit, watch for a back up for the I-80 west exit ramp, we've seen that ramp pretty backed up. LOTS of truck traffic heading west, I-80 is a MAJOR route for commercial trucks heading west! From that split you should have easy going into Iowa.
Good luck, safe travels.
Dan