There are also some cons to consider:
1) In many school districts, your kids won't be exposed to a lot of diversity (my high school, which was of average size in the state, was 99% WASP). This should be less of an issue in Des Moines, though.
2) You're 3-4 hours from a major city if you count KC; even further if Chicago is your idea of a "real" city. I.e., depending on what you and your family like to do for entertainment, it might get pretty boring.
3) Weather...especially if your wife is used to LA.
The diversity issue is not that big of a deal to me, my school was the same way. Your kids will react the way you teach them to.
The big city thing is what gets to my wife the most. I would be perfectly happy with living in a town of 500.
Weather is a smaller issue, we lived in Joplin, MO for a year so she was introduced to Tornado/Thunderstorms and we live in Denver now so the snow wouldn't bother her either.