Not quite Scotland, however, Carlisle has a superb bonfire & firework display, every year (on the nearest Saturday). It`s free and attracts literally thousands of spectators from many miles around. It`s on the Bitts Park, near the city centre, plenty of parking etc.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.