Molly and her family will use the bikes to help with the exercise that is so crucial for cystic fibrosis sufferers to maintain.
Cystic fibrosis brings a build-up of mucus to the lungs and other organs, making sufferers vulnerable to repeated chest infections and other problems.
Exercise keeps things moving and reduces the infection risk.
"It's better for her to be active," Molly's father Lee Macri says.
Molly enjoys cycling with her family into Greytown from their home just outside the town boundary and, once there, inside the grounds of Greytown School.
She carries her doll Rosie as a pillion passenger in a small back seat, being careful to wear her helmet and make sure Rosie has her seatbelt on.
Mr Macri is a secondary school teacher in Wairarapa and Molly's mother Libby Kenny works in local government.
The family moved to Greytown at the beginning of this year and Mr Macri says it "was the best move we ever made".
A doctor told them Wairarapa air was clearer and healthier and Mr Macri said so far this winter the family had kept in better health than usual.
"The kids are healthy and happy, and that's what matters."
Molly was diagnosed with cystic fibrosis around 6-8 weeks old and her condition requires careful maintenance.
She has physio twice a day, which includes breathing exercises.
"I can normally breathe through my puffer," Molly said.
She also has "percussion taps" (on the ribs, to dislodge mucus) for 15 minutes, twice a day - a job for which mum and dad take turns.
The gift, says Molly's father, came at an ideal time.
"She was chuffed."
