Along with his parents Pat Connell, 34, and Jeanna Abelsom, 36, Ronald McDonald House South Island in Christchurch, which provides free accommodation and support to families travelling for their child's medical treatment, has been their home away from home.
And it's been a "godsend", they say.
"It all happened so quickly," said Jeanna. "It was just, 'Go now and worry about everything else later'."
With the West Coast unable to provide the treatment Lachie needs, Pat and Jeanna decided early on that they would base themselves in Christchurch so Lachie would have the best chance. Jeanna parked up her coffee cart and Pat took leave from his job managing a civil construction and maintenance company.
"For the first month, something was happening every day and Lachie had a string of side effects. Every second day, something new had to be investigated and treated," Pat said.
After the intensive first month of treatment, Lachie's body was given a chance to recover.
But in the New Year, a fourth round of treatment will begin again.
"He's doing so well, but he's actually really tired," Pat said.
"He has bursts of energy and then will just crash. He often sleeps 16 hours a day and is often up at weird times but being in this place [Ronald McDonald House] allows that to happen so much more."
They wonder how they would cope if they didn't have Ronald McDonald House, where they will be spending Christmas this year.
"This place has just been incredibly helpful," Jeanna said.
"Coming back here after a day at the hospital, and your meals are cooked, there are no dishes, no stress about housework, you just have this beautiful homely place to come back to."
The couple praised the staff and "small army of incredible volunteers".
"It's one of the places you knew was there but didn't know much about, and hope you never need," Pat said.
"But what they do is just mind-blowing. I have no idea how we could cope without this place."
They've vowed that later on, they will come back to Ronald McDonald House and help out where they can.
"We want to give something back, because they have given so much to us."
Ronald McDonald House South Island chief executive Mandy Kennedy said it costs $1.2 million annually to operate its facilities, including the 26-bedroom Christchurch House, and the Family Rooms in both Southland and Christchurch Hospitals. It costs $140 to provide one night of accommodation to a family in need.
"That is why this Christmas, we are asking the public to spare a thought for families with a child in hospital, and make a donation to ensure we can provide them with a 'home-away-from-home' when they need it the most.
"Ronald McDonald House South Island relies on generous donations from the communities we support to keep our doors open to each and every family who needs us.
"This comes in the form of generous donations from trusts and foundations, businesses, community groups, regular donors and generous individuals."
• For more information and to donate, visit www.rmhsi.org.nz. Ronald McDonald House South Island also an online store: https://rmhsi.org.nz/shop
