Carter's disorder is believed to be the only one of its kind known in the world, and he faces many health challenges.
The appeal, supported by Countdown, raises money for much-needed medical equipment for 11 children's wards in hospitals across the country, including at Dunedin Hospital.
About 70 people, including Dunedin Hospital staff, celebrated the launch of the appeal at the hospital.
Carter's mother, Suzi Helliwell, said her son was happy to serve as an ambassador for the appeal and "we were very honoured to be asked''.
The collaborative appeal was a "great way'' of providing more equipment for the high-tech children's ward.
Equipment already bought this way made a "positive difference'' to having been in hospital for him, for his family, and other southern children, she said.
Another young ambassador, Casey Gordon, attended too.
The appeal has raised $1,022,601 for Dunedin Hospital over nine years. A further $553,265 went to Southland.
