Hi Chale, glad to see you are excited about the ride. My favorite tires I used on the trail are Schwalbe Marahton Plus and Marathon Supremes at 35mm. I have ridden with 23mm tires, but if you hit a soft spot, the 35 mm tires will keep you from going down. If you go in July or August, watch out for goat head thorns. Take extra water and some food. Check out
bikekatytrail.com forum for up to the minute info about the trail and vendors being open or closed. A lot of Wineries open in the summer. Twenty plus wineries within a couple of miles from the trail, some right next to the trail.
Make sure and take some side trips off the trail, especially in Washington, Hermann, Jefferson City, Columbia, Sedalia, and a few others if you have the time and energy. You can also take the Rock Island trail at Windsor to Pleasant Hill close to Kansas City. I didn't get a chance to ride this as it wasn't open until after my last ride on the Katy. Most important thing is take your time and have fun!
Good luck.
Jerry