There is a kids mountain biking trail cut through the woods off of the Manchester Rec Park path between the rec park and Riley Rink. You can find it by entering the wooded path from the northeast corner of the rec park. Look for rules sign on the right about 100 yards in.
Mountain Biking Trails in nearby Dorset
Volunteers have been busy cutting beautiful windy paths through the woods with scenic surprises. As an example, the Humphreys Trail starts with an intimidating short hill but easily gains altitude after that with many zig saggy switchbacks.. You’ll be rewarded on the carved bench with a beautiful valley and mountain view.
Visit the Discover Dorset web site for more details.
Another resource for mountain biking trails wherever you may be: Trailforks