This is a great, moderate hike. We took our 2 children on it (ages 4 & 6) and it was challenging, but rewarding. Hike steady downhill for 3.1 miles to the first campsites, just after crossing a log bridge. The water was about thigh deep in the middle, cold, but fun for the kids to play in. It was quiet---heard very few birds, squirrels/chipmunks, and saw no bears. Also, very few mosquitoes! We saw two groups as we hiked in, but nobody after that. You can hike beyond the riverside campsites, away from the river, then meet up with it again after about 1 mile. We didn't go beyond that, so I can't comment about the loop. The hike out was a bit tough for the kids, but several breaks, using walking sticks, and Mom singing helped considerably. I recommend this hike to anyone wanting to explore this beautiful part of WA---a wild, lush forest close to the Canadian border.
If you're approaching from the south (Spokane area), I recommend driving up past Sullivan Lake. On your return, head north to Metaline Falls for food. There's a nice little grocery store and a park at the end of the main st. next to the visitors' center.