Two 11-year-olds I was supervising took a trail ride at Ride the Ranch (http://www.ridetheranch.com/) this week. They enjoyed their ride, but did not rave about it. They had fun and the 1-hour ride was the right length for them leaving them a bit stiff but not for long.
From what they said, they walked along farm fields and under some small trees. They occasionally jogged. For beginners, they found the ride speed good.
There were about 12 other riders, and 3 guides.
The horses were all healthy-looking, well-groomed, and well behaved. They seem to have lots of horses at the ranch. The stable is very old and somewhat worn, but there is a very new modern indoor riding ring as well.
Overall, I think I would take this age group and teens back to this ranch for another ride.