I wouldn't impose curfews, they'd be near impossible to enforce.
Believe it or not cold water is the solution.
Hose 'em down. Any "youth" out at night...wet them head to toe.
It's cool out, most of them will go running home. If you doubt me, put on some wet clothes and go outside in 60 degree weather.
The persistent ones are the leaders, so arrest them. Easy to id them...they're wet.
Only for the first night. After that, they would dress for the occasion