The popularity of this trip is evident if you zoom in (on the aerial/satellite view) and scan your way down the river. You will notice a great many kayaks on the water or pulled ashore (or on sandbars, etc), either private trips or (far more likely) from an outfitter running trips on this river.
Expect to find numerous areas of shoals, riffles, rips, and even a few solid rapids (though generally nothing too intimidating, after all, they do put dozens upon dozens of neophytes in open-cockpit kayaks on this stretch).
And (having said that), you can get a look at what to expect on this stretch of river from this video of a recreational kayaker's run:
YouTube Vid of Lower Kinnickinnic