A woman with a blood alcohol reading more than five times the legal limit and a man travelling at more than twice the speed limit were both driving with children in their cars, police say.

Both the drivers were nabbed by police in Melbourne' southern suburbs overnight.

Police say a Lynbrook man, 44, was driving at 200 km/h in an 80 km/h zone in Greens Road, Dandenong South with a nine-year-old child in the car on Saturday about 1.40am.

In a statement, Greater Dandenong Highway Patrol police say they were shocked to find the child in the speeding car.

The car was immediately impounded under hoon laws.

The Lynbrook man is expected to be charged on summons with offences including speeding and driving at dangerous speeds.

In an earlier incident, a booze bus station set up on Beach Road, Sandringham, tested a woman that police allege had a blood alcohol reading of 0.269 per cent about 9pm on Friday.

The Cheltenham woman, 45, had two children, aged six and eight, in the car. The woman is expected to be charged on summons with drink driving and other traffic-related offences.