Backyard pubs - aka a shed tricked out with optics & possibly badly stored kegs - are a bit of a daft lockdown project.
It's never going to be the easiest way to hand your guest a drink, but, well, people did do this sort of thing during lockdown.
Still absolutely no reason to let teenagers party without being home.
My 14yo is lovely. She's also friends with the idiot in her year who turned up drunk to a nice 15th birthday party for a dozen kids this week, scaled the party house balcony, pissed on the dancing crowd from above, & was then punched by the birthday girl's elder brother.
Police arrived & arrested both (dd feels this was overkill 🤨). They were very critical of the fact that no actual adults were on site - older brother is 17 & was left nominally in charge.
Or the police might just not turn up. They're over stretched. Then your shed 'pub' gets trashed, or your house gets trashed, or a fight breaks out & no one stops it.
I wouldn't - & I am very relaxed about teenage guests/sleepovers normally, have dealt with the occasional worse for wear teenager, & lose no sleep at all over a bit of a gathering at my house.
It's an entirely different vibe without the householder on site. Don't. REALLY don't.