I am also planning a tour of N. MO this spring. I will be leaving the KC area to Hannibal with stops in Linn county and Kirksville. Most of the roads that I am going to take, I have allready ridden on and they are OK for bikeing. There are parts of US36,US65 and US63 that I will not ride on. Most of the state roads are good.
If you are going to be in of the Amish areas there will be wide shoulders.
The only way to know if the roads are safe for biking is to drive them first, but that takes some of the fun out of it.
South of Jefferson City is a nightmare. I dont know of any good roads to ride down there.
I think
http://mobikefed.org/index.php has some good info. Also there are some maps for bike tours, but I am not sure where they are. You will have to Google them.