Former Papakura mayor Calum Penrose, who chairs the trust, said the project cost multi-millions.
The main donor is believed to be the family of Michael Erceg of the Papakura-based Independent Liquor chain. Erceg died in a helicopter crash in 2005 and a plaque unveiled by Prime Minister John Key on Saturday said the trust was funded in memory of him.
Mr Penrose, now an Auckland councillor, came up with the idea after going out with police on Papakura streets four or five nights a week after becoming the town's mayor in 2007.
The town has the highest proportion of beneficiaries in Auckland and the highest proportion of Maori on the domestic purposes benefit of any district in the country - 28 per cent of all working-aged Maori, or roughly one in every two Maori women.
Mr Penrose said his nights on the streets revealed a core group of 20 to 25 youngsters aged 13 to 14 who were not going to school and struggled with literacy and numeracy.
"I thought 'we need to build an outdoor pursuits centre that will get them into kayaking, mountain climbing, literacy and numeracy - get them into physical things that challenge, motivate and captivate young people'," he said.
The trust has bought the Franklin Adventurous Training School, which runs kayaking, sailing, bushcraft and rock-climbing courses. The school has been relocated to the Papakura site and its founder, Dave Hopkins, has been made the trust's new chief executive.
Corporal Apiata, a member of the Special Air Service based at the Papakura military camp, opened a "Victoria Cross conference room" lined with portraits of Victoria Cross winners.
Mrs Doyle, who was parachuted behind German lines in France at the age of 21 in 1943, evaded arrest until the war ended. She lives in Henderson.