If the kid did ride into the side of the bus, then this probably wasn't the fault of Disney or the bus driver. Unfortunately, that probably won't stop the lawyers and OSHA people.
A similar incident happened at my University. A student was riding her bike on the sidewalk, swerved out into the street without looking, right into a university trolley transporting students. Of course, her parents sued (why should their precious daughter be responsible for looking where she was going?) and the city had to rip up the street, double the width of the sidewalk, mark off special bike paths, and reduced the street to one lane on the side of the expanded sidewalk.
Sometimes it is important to understand that WDW is not an amusement park. It is a city.