It's probably best to avoid this area on weekends unless you're early or late. I was here on a Monday and there were plenty of hikers. The parking area of part of a managed park and it's $2/person for entry. There's also a beach close to the trailhead, if you have some extra time to refresh after your ride.
Family Friendly: Fairly easy riding on the County Park side, or south side. It does get a little steep further up but it is a perfect training area near the lake.
The Liberty Creek Trail
begins as a smooth stroller path and advances to steep switchbacking lung and leg crushing singletrack. There are some fun punchy sections before it gets serious. The decent that's mapped is steep, wide, straight, nontechnical, yet just engaging enough. I rode it as suggested and could see myself doing all sorts of variations depending upon my mood because the trails are so different from each other.