Bluegrass Boardwalk sounds too... bluegrassy. As in the music genre. I for one would never visit an amusement park if I even suspected I'd have to hear banjo and fiddle music 24/7.
Kentucky Kingdom doesn't have the best positive brand recognition, but it's by far the more superior name. Good, consistent ownership can undo any negative feelings brought upon by past incidents.
That said, I wouldn't be opposed to changing it to something more generic in line with their other park... Holiday Kingdom or Holiday Land or something like that.