I feel like this is why the advice is always to consult an attorney. If the law has some easy to fulfill requirement (service policy) then concerned people should have one even if they're only providing access to Uncle Bob and not the general public. It may not be likely that Uncle Bob would cause any trouble (though maybe his computer is infected), but it may not be likely that
anyone with physical proximity would cause any trouble. If you're worried about it then why not do the thing that mitigates the risk regardless?
It's even possible that not providing public access may increase certain risks. If you restrict access and someone guesses/cracks the password and does something terrible, that may make it harder to argue that it wasn't you.
I'm also not sure where you're reading the requirement to identify the users. There are many sites (e.g. Slashdot) where users can post anonymously (and via Tor or equivalent). Are you saying they don't qualify?
They have some info here:
https://openwireless.org/myths-legal.html
But notice that half the page is dedicated to extra-legal ISP shenanigans, which brings us back to routing your whole internet connection (guest net included) through a VPN. Which, again, you probably want even if you're the only one on your connection. It's not as if copyright trolls are renowned for their accuracy in targeting only people who are actually infringing something.