This article was reproduced with the kind permission
of the British Broadcasting Corporation
21 November 2007, 20:59 GMT
They were passengers in a grey Renault Megane car travelling along Preston Road, Yeovil, towards the Asda store.
A blue Peugeot 306 was waiting to pull out of Stratford Road into Preston Road when its front seat passenger launched the firework at the Renault.
The offender is described as a white man, in his late teens or early 20s, with short dark hair.
An Avon and Somerset Police spokesman said the Renault was dented and damaged as a result of the "reckless incident".
"There were two young children in the car who were left very shaken and distressed as a result.
"Had the firework gone inside the Megane, those children could have suffered serious injuries," he added.
Detectives are studying CCTV pictures taken at the time.