Come on and join the bike ride. If you can get others to join you that is even better!
The point of Hike and Bike is just getting people out to socialize and do some exercise at one's comfort level.
(Speaking of that, a good comfortable bike seat is essential on this slightly longer journey.

)
I just have an old Pee Wee Herman type of a 3 speed bicycle and pedaled it on the past 4 rides.
I don't ride very much either but there was little difficulty with a similar 15 mile route to Iroquois Park last year.
(Even at my advanced weight and age

)
It appears this Labor Day route will run down 2nd Street, loop around Churchill Downs, and continue to the Iroquois Park turnaround. No one is obligated to complete the entire route and there are safe and closer turnarounds marked on the map.
If a bike needs some minor tweaks there are some bike "doctors" available around 9 AM on Monday at Waterfront Park and later at Churchill Downs.(No charge for this service!)
Overview of the 18.46 mile Labor Day bike ride:
http://tinyurl.com/5jxeua