Here is a video of Erwin Park. Check it out before you drive all the way to the trail.
How much riding is there in McKinney?
What the hell is an aluminum falcon?
At Erwin Park there is 7.6 miles of singletrack. All excellently groomed and maintained. Difficulty level is about a 6 out of 10.
It's a great trail. More info here: Erwin Park Mountain Bike Trail in McKinney Texas
When I'm not riding I help beginner mountain bikers learn new skills at Texas Mountain Bike Trails.