I have looked up several commercial trips, and I a seeing most give some discounts to kids. One company (on the Yampa) listed kids 10 and under were free with a paying adult, 11-12 were 1/2 price. Other companies I saw had a 25% discount for kids. But it looks like most give some sort of discount.
Boy, am I glad I have my own boat... commercial trips are expensive
Taking kids on a trip can be a great experience, depending on the trip and the kids. That being said, I didn't take them on my first GC trip. That just means I have to go again to take them