I'm considering volunteering as a mechanic/bike helper in my area. Has anyone here experience from something similar?

I see badly kept bikes all the time, especially kid's bikes, and it makes my fingers itch. It would take me 15 minutes tops to make many of these much nicer to ride, just by lubing the chain, adjusting the brakes and topping up the tires. Oh, and adjusting the seat post to a good height. Many parents around here buy bikes for their kids but don't ride themselves, and I'm guessing they're just a bit clueless about normal maintenance. And as a total stranger I can't just walk over to some random kids in the neighbourhood and start complaining about their bikes ;-) I have a grown kid myself, so I don't know the younger ones any more.

So I'm wondering how to arrange this. I'm thinking one evening a week for a month, because it's easy to remember. "Bike Tuesday", every Tuesday in May, for instance. And I'll be at home, where I have a bike stand and all the tools, so it'll be strictly local. I want it to be very very low-key, so that kids will feel comfortable just wandering by if they're curious. So no phoning ahead for an appointment. But - that means I may end up with a frustrated line of ten kids who turn up at the same time. And I'm only one person, so there's a limit on how fast I can work and how many bikes I can take.

Any ideas on how to arrange this in a sensible way, without making it too formal?

(I tried holding a maintenance course for teenagers once btw, which was hugely frustrating, as they expected to be entertained and allowed to interrupt and do other stuff throughout. I am not a born teacher! I ended up reading the paper and telling them to ask me if they wanted to learn something.)