Invest in a portable DVD player with multiple screens. It will be your saving grace. Modern, technologically savvy children quickly tire of "I spy".
Avoid Chicago, at all costs, especially with small, potty trained children, unless you're crazy, or feeling really adventurous. Keeping them occupied with the above mentioned DVD player may save you from having to take a potty break in downtown Chicago, you know, if you're feeling adventurous.
If you're planning a picnic lunch at a rest area, just forget the whole state of Illinois. Apparently, a "rest area" in Illinois is actually an "oasis" consisting of an exit ramp with a gas station and strip mall type set up with multiple eating establishments. Not a picnic table or grass in sight. Rest areas with grassy areas are essential when traveling with children, or pets, for that matter.
There were actually four kids in the car. Number 4, however, is leaning over in the seat on the left to avoid having his picture taken. Tanner and Tatum were actually playing together, without fighting. Miracles do happen.