firework

放烟花 翻成英文是 light the fireworks.
letting off fireworks.也对的

其它的表示方法

烟火
beacon
fireworks
protechny
pyrotechnical
rocket
firework display

firework display [简明英汉词典]
焰火
protechny [简明英汉词典]
n.烟火, 烟火的施放
pyrotechnical [简明英汉词典]
n.烟火,烟火装置(材料)

应该是fireworks吧 放烟花 have displays of fireworks
例句与用法:
1. 庆祝会的高潮是燃放烟火。
The climax of the celebration was a firework display.

2. 男孩子在放烟火.
The boys were letting off fireworks.