The kids will have a great time if you let them be kids.
Keep them dry, warm and feed.
Don't yell at them. Don't get upset with them. Be firm and clear on the safety rules.
If you don't get stressed and don't fight or yell at others on the trip, the kids will have an amazing trip!
Make sure to keep the days very, very short. Be flexible, and change itineraries if you have adversity.
Good luck! We've had a lot of amazing trips with my kids, now 15 and 12. Just finished 5 days on the Yampa river, as we work up to harder and harder water.
Gravity