we've decided we will make the long drive in one day with four people rotating at driving.
Please read this article carefully, as you will be doing what's called a "speed run". You will probably be on the road for at least 15 hours, so I'd leave around 4 am. Try to hit Chicago after rush hour but before dark. Trying to find your way around an unfamiliar city after dark can be difficult, and as with any big city, there are areas where you should not go, especially after dark. Coming in from the south, you will be going right through those areas.

Safe free parking anywhere near downtown Chicago essentially doesn't exist.