Some suggestions from someone that went a similar way last summer.
1. Do NOT drop down out of Detroit or on I-69 to 80/90 through Indiana. For what you have to pay, it is rough as a cob (especially the bridge aprons). Just terrible.
2. I-80 through Iowa is one long truck. They will be constantly passing you (if you drive 65 or lower like you should).
3. If you can add a day to your trip out, US-2 through the U.P. of Michigan, Wisconsin and Minnesota is a much nicer drive. You could then drop down I-35 to I-70.
4. Or take I-69 south to Indianapolis. Follow the bypass north (less busy) around the city to reach I-70. And avoid the Chicago nightmare altogether.