Each time we go camping I make sure we take the kids on an easy, kid-friendly hike in the area, that provides enough elevation gain to make them work out a bit without whining too much. This time we were staying at Lincoln Rock state park on the Columbia River near Wenatchee and I found this hike to the two lakes next to the Mission Ridge ski area, 3.5 miles round trip and about 900 feet elevation gain, just the kind I was looking for.
All kids (ages 4 to 8) had a pretty good time on this one and entertained each other all the way up and down the mountain. There was some whining, not about the hike being too hard, but about who didn't want to play with whom.
Once we got to the lakes the kids liked exploring the shores so much the adults had to convince them it was time to leave. When we got in the car for the drive back they instantly passed out. Another successful outing!