I would take the IL route 57 way over In route 65. While technically longer in mileage, we have always moved quicker time-wise and stress wise this way. I do have to say...IL is ONE long state! It seems like forever, and then bam! YOu are thru KY and TN in no time! As far as stops go, we leave from just west of Chicago, and stop overnight generally in the Marietta Ga area...sometimes we make it to Valdosta, but not usually. We do basic stops along the way as needed...if daylight when we hit Chattanooga we do like to stop and stretch and take in the sights of the hills. Our kids are older, but we had a portable DVD and game system set up for them last trip, and DD loves to draw so that keeps her busy. DS was 9 1/2 at the time and we did fill a small contailer with legos...he made pretty decent use of those. We have a minivan so also having the kids split into their own row of seats part of the time helped. The trip down was not bad, but we went in December...and coming back home, watching the green and floweres disapear from the south and see the brown and grey of the North...blechhhh, it was so depressing. Luckily you won't have that issue in June.

We just came back from the WI Dells and the kids thought it was nothing, about 3 1/2 hours from here. Depending on the ages of your kids there is a variety of things to keep them busy. Cards, sticker books, cling stickers for the car windows, coloring books, "barbie goes to WDW", gameboy, reading, books on tape, once, DD brought fabric pens and decorated a t-shirt along the way....I would ask the kids what things have they been needing a long time frame to do and write down the suggestions, then stock-pile what you will need. The good thing about driving is you have room to pack stuff and it is accessible...the bad thing about driving is you can pack TOO much stuff and are overloaded! I would absolutely have one small suitcase that has all of your overnight stuff in it for when you stop for the night. Not sure if you take all your stuff into the hotel or not, but it is so much easier to have thekids stuff available and they can get ready for bed while you and your DH unload the other stuff or rest! We allwed enough time on the return trip for the kids to swim a bit at the hotel (indoor) it helped to take the sadness out of the return.
Have a great trip, June is just around the corner!
Pam