Lewis, now a 67-year-old pensioner, had offended for his own sexual gratification, with no question of consent, given the age of the children, Judge Michael Crosbie said.
He sentenced Lewis to six and a-half years' jail for sodomising a 9-year-old boy 17 years ago, sexually violating him over a period of about two years and for indecently assaulting an 8-year-old about 20 years earlier and committing numerous indecencies in her presence until she was about 14.
Both victims had been severely affected by what had been done to them, the judge told Lewis at sentencing in the Dunedin District Court.
The pre-sentence report indicated little remorse from Lewis, apart from for his own loss. He was unable to consider or take seriously the impact on children of being abused by an adult. That was because he was "a predator", the judge said.
Crown counsel Craig Power pointed to the significant age difference between the offender and the victims; Lewis was 23 years older than the girl and 40 years older than the boy at the time of the offending.
There had been an element of "grooming" in relation to the ongoing sexual violation of the boy and the first offence against the girl had been committed when another child was present.
Both victims had been very young and had been significantly and detrimentally affected, Mr Power said.
The now 27-year-old male victim talked of feeling intimidated, threatened and embarrassed.
He believed the offending and its effects were a main reason behind his substance abuse and psychological problems including self-mutilation.
His mother talked of him being "broken" and, from the psychological report, it appeared that was not going to change, Mr Power said.
The girl spoke of how the offending had affected her trust of adults. She had tried several times to talk about the offending but had not been listened to.
She still had nightmares and believed her life and education had been significantly affected.
Defence counsel Sarah Saunderson-Warner said the male victim clearly already had difficulties before the offending.
While some of his difficulties could be linked to the offending, others could not, counsel said.
She accepted the pre-sentence report said Lewis appeared not to have expressed any remorse, but said he was someone who had trouble articulating how he felt.
He accepted his actions had a detrimental effect on the victims.
His way of dealing in recent years had been to remove himself from contact with children at every opportunity. He acknowledged he needed help, and that what he did was wrong.
Judge Crosbie told Lewis there were two physical victims, but more, if the families were included.
There had been real harm and loss to both victims.
They had effectively been in his care and he had breached his authority and their trust. The boy already had problems.
The offending was premeditated and an aggravating factor was that Lewis had three previous indecency convictions from the 1970s and 1980s and one in 2003 for possessing objectionable material.
Given his age and his health problems, Lewis might well end his days in prison, the judge said, sentencing him to six and a-half years' jail for sodomy, with concurrent terms of three years for sexually violating the boy, two years for indecently assaulting the girl and one year on the representative charge of indecent acts against the girl.
The judge acknowledged no amount of money would fix what Lewis had done to "these young people".
He said New Zealand did not have cheque book justice but there had been various expenses and costs incurred by the victims and although Lewis had offered nothing, he "should pay something".
He was ordered to pay $5000 reparation to each of the victims.
