Let's face it—Byron is a fool for most of The Watsons Go to Birmingham—1963. He seems to make the dumbest decision possible every chance he gets, which means he's trouble all the time. But it's not just about getting in trouble; some of Byron's choices are so foolish (um, playing with matches in the house, anyone?) that they could have dire consequences. And that's exactly what Momma and Dad are afraid of if Byron keeps it up. Finally, Momma and Dad decide they need to do something drastic to scare Byron straight—and that's where Grandma Sands and the trip to Birmingham come in. And sure enough, the trip does get Byron into shape, but not in the way anyone expects.
Byron is a bad influence on Kenny, and Kenny makes bad choices only by following Byron's example.
Being foolish is a necessary part of growing up. You can only learn from your own mistakes, so Kenny's foolish choices have nothing to do with Byron's influence.