While on the NU, take the family, drive 12 miles up Steamboat Creek, and stop at the Fishwatch trailer. Head down the path to look at the pool. By early August there will be hundreds of steelhead in the pool, protected by my friend and Fishwatcher Lee Spencer. Lee is a fascinating guy, and will educate all regarding the life histories and trials of NU steelhead, plus other interesting topics if you wander there. He's an archeologist by training, and if you are real nice and your kids are careful, he may show you one of his atlatls.
If, after the visit, you found the side trip worthwhile, consider a donation to the NU Foundation.
One other thing...don't have high hopes for numbers of fish. Be very pleased if you hook one in your time on the river. The river is tough and popular, and August can occasionally see some serious heat and warm water. It is an even more difficult river for kids, because the wading can be a serious challenge, and short stature can be a significant disadvantage. But is a great and beautiful river, and it is entirely possible that you and/or your kids will find success with the fish. Just don't go in with the illusion that because it is a great river you will find steelhead at the end of your line. Everybody that fishes it gets skunked on the NU at one time or another. Though I know the river pretty well, I still get skunked most of the time. Of course, I am very particular about where and how I fish (the people concentrate where the fish concentrate, and I head where the people aren't), but the point is that it is tough.