If I was going to ride the trail and had to leave my car at the east end for an extended period, these are the possibilities I'd consider:

Portage des Souix: 2.5 to 3 miles from Machens. Has a marina, St. Charles Co. Library, Yacht Club, Tavern, Post Office. Payne Road or Kinghammer Rd to 94 (very short distance on 94) to Machens Rd.
St. Charles/Smartt Field airport- 8.5 miles from Machens. Restaurant, small airfield, Confederate Airforce museum. Parking. Portage Road to Portage des Souix, then as above.
St. Charles. Do out and back.
It's really a shame that the Grafton Ferry is not in operation anymore- just across the river from Smartt Field is Grafton, with B&Bs, hotel, Pere Marquette State park, and the western end of a trail/trail system that will take you through Grafton, Elsah, Alton, the Chain of Rocks Bridge/Route 66, all the way to the Gateway Arch and St. Louis.
There is a route from the east end of the Katy, back towards St. Charles, across the Mississippi via ferry, then across the Illinois by ferry (this is an absolutely beautiful ride) to the above mentioned trail, if anyone is interested. It's not an easy ride, but it is pretty spectacular for the climbs and views.



link to google map