The victims received serious facial and head injuries. One was hospitalised and has since returned to England. He is receiving specialist treatment for damage to his left eye.
It is understood both victims had been working in Wanaka for at least a year.
Of the remaining nine offenders identified by police, one is from Dunedin and has yet to be found and interviewed.
Eight others are from Wanaka, have been interviewed and will be dealt with through the police youth aid section.
The exact action to be taken against the remaining nine offenders had yet to be determined, Const Vink said.
Police had identified that they had a "lesser role'' in the assault and decided not to arrest them.
"The reason for arresting [the three] is we do not want this to continue,'' he said.
