I've never seen the rule that says you're not allowed to enjoy your work, but that's by the by.

If you're providing any sort of good or service (including a performance) for which you are receiving payment, then the US government will, quite reasonably, assess that you are working. As such, you'll need to get a permit.

Trying to claim 'It's not really work, because I'm enjoying myself' will be unlikely to succeed in the event of an appeal.