Rolls are to be completed this month, and some of the association's members headed to Zorb on Saturday to get the ball rolling.
Seven people chose a course to roll down, including fieldworker Michael Schneider, from Auckland.
His son has one of the rare conditions which falls under the association's scope, and he said the event was to raise awareness.
"We just want them to have the best chance to have the best life they can."
He said the Zorb experience, which was his first, was good.
National executive chairperson Trevor Jenkin said there were about 2000 members in the association, with a few in the Bay of Plenty.
He said the event, which went well, was postponed last year. Zorb sponsored the event with free tickets.
While it had been "pouring" with rain, those at the event still managed to have a good time, he said.
"Even watching the supporters gives them a sense of encouragement."
More events are to be held in other parts of the country during September. This included a picnic in Hamilton on Sunday.
All the funds raised will go to the region they were collected in to contribute to the
continuation of connecting members through events, led by the local branches.