About 50 years ago when I was a cub scout, a neighbor who was a controller at JFK (then Idylwild) took some of us to the airport to show us around the tower and then the larger facility off the airport grounds that handled a wider area. I still can vividly remember the large, dark room with these huge round radar screens set flat like tables, and the small clear plastic "boats" the controllers used to identify the blips for each plane they were handling. Very low tech compared to today. I can't recall whether any of the kids were allowed to communicate with any aircraft, though in those days I doubt it would have been a big deal. But I can say I was thrilled by the experience.
It's apparent from the recording, that none of the parties involved felt disturbed by this event, and in fact all seemed to enjoy it. As far as where the line would be on this type of activity, I think what transpired here was nowhere near wherever that might be. But I'm sure the anal authorities will probably come down hard on the offending party, if for no other reason than to discourage any future copycats.