OK, I stand corrected about Avenue of the Saints; I haven't had much reason in the past few years to go up as far as the Iowa line, and so I was unaware that the road through the rural areas up there had been widened and made limited-access. My apologies.
As to what to see near I-70 in Kansas/Missouri, there are a few things you might like. You can visit a number of excellent wineries in the Hermann, MO area about 70 miles west of St. Louis, and there is a zipline attraction near there as well. You can also see a large section of the Berlin Wall that has been installed as a memorial on the campus of Westminster College in Fulton, MO.
http://www.churchillmemorial.org/highlights/Pages/Breakthrough.aspx
(Not many people realize this, but Fulton was where Churchill actually delivered the famous line about the Iron Curtain in a 1946 speech.)
Kansas City of course has some serious barbeque worth investigating, but there are also the Nelson-Atkins Art Museum
http://www.nelson-atkins.org/, and the National WWI Museum (which is outstanding!)
http://www.theworldwar.org/s/110/new/index_community.aspx. The biggest special event of the year in KC is the American Royal in the Fall, it is one of the largest livestock, horse show and rodeo events in the US, and stretches out over about 8 weeks of special performances and shows. Several big name country artists do concerts as well.
There are also a couple of large waterparks, a Nascar track if you enjoy races, and of course, there are major football, baseball and hockey franchises in KC and St. Louis if you would like to attend a game, depending on the season.
BTW, if you are wondering what kind of scenery a particular highway in the US will let you see, there is a website that has lots of highway driving photos from all over:
www.aaroads.com