"But if you spend any time in a children's ward you learn there are people with bigger issues."
He said the first sign was Hunter becoming lethargic and drinking a lot of water. "He got more and more gaunt. He was misdiagnosed at first, but on that weekend he looked so emaciated we took him straight to the children's ward.
"After a blood test, a doctor told us he was diabetic - which we knew nothing about."
Youth Diabetes case workers were fantastic, he said, guiding the family through what to expect. "There's the whole thing of being different and having to shoot up. I injected him the first time and after that he did it all himself. He was really amazing. He basically took charge."
Sainsbury recalls a couple of times when Hunter experienced a frightening drop in sugar levels, including on a disastrous family skiing trip.
"The brand new 4WD broke down and he suddenly started acting really strangely. We thought he was just goofing around but it was actually a massive low and we had to get a glucose shot into his thigh."
He said the incident also proved an eye opener for his twin sister and her friend. "I think they sometimes thought we were easier on him, and suddenly they saw the fitting and stuff and it was real to them. Not just a sympathy card, but very dangerous and frightening. It made everyone realise just how serious it was."
Of all people with diabetes, it is estimated about 10 per cent have type 1, which most often occurs in childhood but can occur at any age. Early symptoms include thirst, passing more urine, weight loss, being very tired and mood changes.
Sainsbury says Hunter, who recently returned to Wellington after time in the Northern Territory with his sister, gets an eye test every year and keeps a close watch on his circulation.
Sainsbury insists children with type-1 diabetes can live a regular life but stops short at describing it as normal - and says as a parent the concern is always there.
"Even when they leave home you can't help but worry about what will happen if they don't eat, and what if they have a low," he said. "But at the end of the day they have to manage it themselves. You can't sit and watch them 24 hours."
Sir Bob Jones will be the guest speaker at Saturday's fundraising dinner. The proceeds will support local children and teens with type-1 diabetes.