"There are a whole lot of processes that need to be gone through before you come back to court," Judge Bidois said.
He stressed to the trio's families the importance of the family group conferences.
All three will remain in Child, Youth and Family custody until March 7.
A 17-year-old man also charged over the Boxing Day attack is on bail until March 19 when a case review hearing will be held. Mark Wikotu, 18, is in custody until May 7 when he will be sentenced on charges of aggravated robbery and unlawfully getting into a motor vehicle.
The German tourists - a 19-year-old man and 18-year-old woman - were camping near a skatepark at the intersection of McAllister and Beach Streets when they were attacked in the early hours of the morning.