Since we have our own horses, we have trailered them to Red Rock Park several times for charity/group rides.
One outfit I am aware of is "Cowboy Trail Rides". It is family owned and they are very, very good to their animals.
Here is their website (hold onto yer reins podner, it ain't cheap!)

www.cowboytrailrides.com

If you have not seen Red Rock Canyon yet, it is very stunning...amazing that such a beautiful place can be so close to Vegas!

Remember, don't squat with your spurs on!