My boy and I enjoy riding these trails, just casual and not crowded with other riders. We like the little rollers and the casual exploring next to the river.
On Strava we put in a surprising 7 miles in this area just casually cruising around.
Start at the park near the Riverdale Civic Center and head south down the paved path, take any one of the dirt turnoffs.
Strava for directions
https://www.youtube.com/watch?v=kvrJ5NNqv0Y