We drive from the IA/IL border (Davenport area), we've done it three times and will be doing it a fourth in April. Here are a few things I've gathered from our trips:
1. Don't leave the interstate in IL trying to cut straight south through the state...may not apply to you, but I travel with a lot of kids and rest areas and bathrooms that are open 24 hours sure beats gas stations in small towns that are closed

2. Time your trip to go through Atlanta in the late night or very early hours if doing so on a weekday. It gets uglier than any other city in the US during rush hour (5/6am-10am and 3pm-6/7pm). When going through, just go straight through, no bypass. Get in the diamond lane on the left (carpool) and go...it helps you to not go crazy as people weave around...I'm from a small town, you are from Iowa so I can assume a small town

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3. plan on letting kids out to the bathroom with each gas stop...not optional unless maybe sleeping. Stop at a rest area or two so they can have races around a random tree to get them moving.
4. have some idea where you want to get to and have some ideas on hotels you could stay at...you won't fit in some single hotel rooms so pulling up to a lonely exit at 2am with one or two hotels that don't have accommodations for your family really is no fun...we've done it.
5. If you have a smartphone, download and use iExit, you can search upcoming exits for points of interest like restaraunts and gas stations, it even tells you how far from the interstate each thing is...I hate nothing more than to see a restaurant on the sign, exit for it and then find it is 3 miles from the interstate through construction (done that before as well, wasted almost an hour to get to a freakin Burger King).
6. Electronics for the kids (for your sanity)
7. Goodie bags. We get cheap toys (sometimes a new video game/movie) and non-messy treats (airheads, tootsie rolls) and put them in paper bags that we label. Every hour or two (or when we just need it) we announce that it's time for a goodie bag!
More for the larger family stuff at
http://www.disboards.com/threads/large-family-tips-and-discussion.3138060/