I pretty much always have an ukulele when I travel. I will often play quietly, and refrain from singing, when I have time to kill at the airport. If there are many people around, I will not play or move to a less crowded area.
It is a real shame that Led was asked to stop playing at Honolulu airport, I cannot imagine that happening at Kona, Hilo, or Lihue - not sure if someone complained or if the guard was just worried that his boss would see that he was not 'enforcing the rules' and get in trouble.
Yes, there is the Hawaiian Airlines lounge with live Hawaiian music at the Honolulu airport so clearly there are SOME places that music is allowed to be played.
Hopefully they will figure it out.