Registration starts March 1st.

https://mostateparks.com/2013-katy-trail-ride

The 13th annual Katy Trail Ride, June 17-21, allows bicyclists to experience Katy Trail State Park from Clinton to St. Charles. Missouri State Parks and Missouri State Parks Foundation invite you to join them on this scenic five-day ride on the nation's longest developed and most popular rail trail.
This year's ride covers approximately 253 miles of Katy Trail and features great food and many fun activities. Hot showers are available at each overnight stop, enhancing comfortable campsite settings. Participation is limited to 300 people so register early to ensure your place on this scenic ride. Registrations will be accepted until May 1 or until the 300 maximum limit is reached.

I just registered and it cost me $370 which included the ride, two meals a day, a shuttle bus from St. Charles to Clinton ($60), and a shuttle bus to a hotel on one day ($20). Not a bad deal. This will be my 3rd straight year doing this ride.

The trail is crushed limestone. People do it on skinny-tired road bikes, but something with fatter tires like hybrids, cyclocross, touring, or even mountain bikes are better. Actually the mountain bike may be overkill.

Mountain bikes work well if you want to ride just off the trail.
Otherwise, you're correct. You don't need really aggressive tires.

All filled up after only 5 days! Last year it took until April to fill up.

Rain, skinny tires, and crushed limestone don't mix. I got caught on the Madison County Trails in the rain and it wasn't fun. This sounds like a fun event.

We were on the Katy this weekend and rode out to Cooper's Landing and ate at Chim's. What a fantastic trail and can't wait to get back there. As a side note, it did rain some, but the two folks in our group with road tires had no problems at all. My wife and I just put on randonneurs, so our ride was very stable.

Mark down March 1st, 2014 on your calendar to go to https://mostateparks.com and search for the 2014 Katy Trail Ride. The ride filled up in 4 days in 2013. It will be starting from St. Charles, MO in 2014 which means it's a few miles closer to Ohio.