Fireworks dont have the height to cause any problems unless they are set off near to the runway ends.
At Manchester Airport there is a school about 1 1/2 miles on the centreline of 23R They used to have large commercial fireworks that were coordinated with arrival gaps, not sure if they still have the display.
The fireworks are very visible from the air but not as dramatic because they have all the town lights in the background
What used to cause problems were the "liberated" military parachute flares that were very high.
One of the highlights of my flying career was being airborne over Manchester city centre at the stroke of midnight on the millenium. In an instant the area was illuminated with thousands of rockets for as far as you could see in every direction, absolutely awesome
