All those arrested are believed to be from South Auckland and it has not been established what they planned to do in Hawke's Bay.
The 53-year-old man, who was robbed of his vehicle and assaulted in Manurewa on Tuesday night, was taken to Middlemore Hospital with moderate injuries, police said.
Circumstances surrounding the attack are still being investigated.
All seven people were in custody overnight.
The 13-year-old boy was in Child, Youth and Family Service care, while two 16-year-olds - a girl and a boy - appeared in the Napier Youth Court yesterday afternoon.
Four other people aged between 18 and 22 are due to appear in court today.
The 16-year-old girl, who is understood to have previously been wanted by police in relation to other matters, sought bail and gave a prospective residential address.
A police officer told Judge Tony Adeane yesterday that the South Auckland address had been checked and it was actually a shipping yard and not a residential address at all.
Bail was denied and the girl, with the other youth in court, was remanded in Child, Youth and Family care to appear in Manukau Youth Court this month.
Police said they were not seeking anyone else in connection with the incident.