A Melbourne man whose wife and two daughters were mowed down by a hit-run driver last week has said his young family's lives have been changed forever – but is thankful they are all still alive.

And Brad Nash said his eldest daughter Tayla, 9, would not have survived the ordeal but for a quirk of fate.

Tayla, her seven-year-old sister Chelsea and mum Michelle were coming home from school in

Officer, near Pakenham, last Friday when they were struck by a ute along with five other children in a scene that witnesses likened to a "bomb site".

Michelle and Tayla took the brunt of the collision, Mr Nash said.

That fateful day happened to be what he said was a "bit of a show-off day" for Tayla – and that's exactly what saved her life. Normally Tayla would have been coming home on foot. But not last Friday.