My underage daughter's friend invited her to go to gym with her for one day

My underage daughter's friend invited her to go to gym with her for one day. Because she's underage, she must be accompanied by a legal guardian to fill in a form. That I understand, but now thet require a copy of her ID or bith certificate to god only know what to do with. If it was for a contract, then yes I understand. But a single day pass, no freaking way. If that's how you conduct your business, then good luck.