The couple have spent nearly $300,000 over the past two years trying to replenish the cliff's shrubbery.
Mr Coote, a 71-year-old chartered accountant, hired engineers who examined the damage to the cliff face and said the trees would have needed at least five years for their roots to take hold.
"There wasn't enough time for the trees to set their roots in, so they weren't able to suck the water up from the rain the night before," said Mr Coote.
Huge downpours from multiple thunderstorms on Thursday night last week caused part of the land at the back of the property to slide down the cliff and into Hobson Bay.
The Parnell house and surrounding properties suffered no damage but it is now only held up by one wall, and a second wall to prevent further damage could cost up to $100,000.
"The only compensation we will get will be from the earthquake damage fund [EQC] but that will only be fractional of what it will actually cost to fix."
The Cootes were appalled by the behaviour of the children. "Not one parent came and said sorry to us," said Mrs Coote. "Boys will be boys, we're not silly, but a sorry goes a long way.
"We took it up with the parents but they weren't even interested in bringing the kids around to see the damage they'd done."