An alleged drunken driver was unable to leave his hospital bed and be in court to face charges for killing a young mum and her toddler in a head-on smash over the weekend.

The 19-year-old accused was due to appear today in the North Shore District Court on two charges of driving with excess breath alcohol causing death, and one charge of failing to stop at the scene of a fatal accident.

However, the duty lawyer told the court he had spoken to the man in Auckland Hospital but the accused was not in a fit enough state to give instructions and unlikely to be released from hospital this week.

In the teen's absence, Judge Nevin Dawson remanded the accused in custody at the hospital until next Monday when the case will be called again in the Whangarei District Court.

The 19-year-old was also granted interim name suppression.

A Northland mother and her toddler were killed, while another child was seriously injured, when their vehicle and another car collided head-on along State Highway 1 near Oruawharo Rd in Topuni about 9pm on Saturday.

Early police investigations revealed the 20-year-old mum from Kaiwaka, her two children - both aged under 3 - and a man were travelling north.

Two people heading south were in the other vehicle that was involved.

The driver of the southbound silver sedan allegedly failed to stop and was located and arrested near Auckland with another person who was in the car at the time of the crash.

The seriously injured man in the northbound car was also airlifted to Auckland Hospital by the Auckland Westpac Rescue Helicopter.

The injured toddler was flown to Starship children's hospital in a serious condition.

Diversions were put in place through Mangawhai, and SH1 in Topuni was closed until 3am yesterday.

The police serious crash unit examined the scene and investigators are appealing for witnesses to come forward.

Detective Sergeant David Hamilton said people driving on SH1 on Saturday evening, particularly in the Maungaturoto and Kaiwaka areas, who saw the silver sedan before the crash are asked to contact police.