So, would you be willing to sick thugs to collect a fee from the head of the household, who allows collected friends of the 5 year old kid to sing 'Happy Birthday'? After all, royalties are due.
If it were my copyright? I'd bring an aluminum bat.
On second thought, no. It would be bad publicity to show thugs breaking down the door all because the head of a household let a bunch of 5 year olds sing 'Happy Birthday' without paying. Might even motivate soccer moms to form a lynch mob. Now that would be interesting.