Two other children in the station wagon, aged 12 and 13, survived but were seriously injured.
At least one person was trapped in the wreckage and had to be cut free by volunteers of the Kāeo, Kerikeri and Mangonui fire brigades, who also provided initial first aid.
Senior Constable Warren Bunn, of the police Serious Crash Unit, said the collision occurred a few hundred metres north of the former oyster processing plant on a straight piece of road.
The weather was fine, both vehicles were relatively new and in good condition, and everyone was wearing a seatbelt.
The investigation was continuing but driver fatigue was a possible factor, Bunn said.
The head-on collision occurred on an open road with a 100km/h speed limit.
The crash forces would have been enormous, he said.
