I assume you’re not considering taking I-80 all the way to Chicago, because that’s really out of the way, but that’s a cool city (but relatively expensive) to spend 2-3 days during a week’s drive.

You’re likely going to hit StLouis either way, and that would include the Arch, Chahokia mounds, Ted Drew’s, Cards and The City Museum.

If you go on I-80 and go down the river to StL, spend a half day in Hannibal.

KC has the Plaza and a handful of church history.

Honest answer, unless you Reeeeaaaly like long talks with your fellow travelers, find a way to fly to Nashville for 2-3 days and drive from there.