How about the Salmon River ("of no return")in Idaho? Ran it with 3 teenagers and camping gear in my alumaweld a few years ago in Aug. River was low (about 3000cfs) so some of the big class IV rapids (Big Mallard, Vinegar etc) were easy but some of the others.. Elkhorn etc were rocky and technical. Had to pull one of the rafts in our group off a boulder wrap in Growler. Toughest spot for us was Salmon Falls which is normally a class 3 but the easy side was high and dry. We went down the toughest side which is two big drops with a huge hole in between. Friend took a great picture of us hitting the hole where you could only see me from the waist up and the stern of the boat...everything else was buried in white! Had about a foot of water in the boat but everything and everybody stayed in. 100 miles of whitewater in 6 days...not great fishing that time of year but a great experience.