MCI decor is throwback to 1977, while the Admirals Club has a late 80's feel to it. Although construction has begun to improve the place, you don't want to be stuck there too long.
5 hours @ MCI gives you ~3 - 3 1/2 hours in the city.
If you like history, the Steamboat Arabia Museum is facinating. A steamboat carrying tons of dry goods sunk on the Missouri River in 1856. It was preserved in mud for over a hundred years, then dug up. This place has the contents.
http://www.1856.com/
The Country Club Plaza is the first shopping area built for cars. Tons of shops, free parking, and eating. Many good restaurants.
http://www.countryclubplaza.com/ http://www.prainternational.com/dokci.htm#Restaurants
If you like Barbeque, there are several great places in town: Arthur Bryants is famous; KC Masterpiece is popular; Jake Edwards is nearby the Plaza.
Other museums: Kemper -- modern art, free; Nelson-Atkins -- various art.
A 1-day car rental may be less expensive then round-trip shuttles or taxi. Avis, Hertz, National, Budget, Alamo, Enterprise are all near the terminals.
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He who dies with the most miles ... is dead.