Personally, for those who can't pronounce it correctly, I'd prefer keen to coon.
Keen comes a lot closer to the ü sound. For the rest of the name, just think of Huckleberry Finn.
Actually, I don't see it like this whatsoever. 'Coon' or 'Cuen' is more understandable for a native English speaker in trying to grasp what a 'K[ü]hn' sounds like.
'Keen' is pronounced in English as a German would understand 'Kien' and unless you guys are referring to some Bavarian accent I'm not quite familiar with, he's not "Kienhackl" in German.
Coon-hawck-el is surely about as close as a native North American English speaker is gonna get to pronouncing his name correctly.
As for the player, he's headed to Windsor, so this is the year he really gets to show his stuff - or not.
Last season he thought he'd spend the year split between Augsburg and Landshut. He only played four games in Augsburg. He did fine in Landshut playing against men, but he had a lot of little injuries. Maybe his tall frame just didn't yet have the muscle to absorb a lot of the abuse he was getting, especially as the son of the great Erich Kühnhackl?
We'll find out what kind of player he truly is soon enough.