"They never complain about anything, they just get on with giving William the best loving environment any child could wish for."
Mr Huijs said it was an "unusual feeling" to be getting help when there were other people in need as well.
William was born 10 weeks prematurely, has a hole in his heart, has a club foot, has underdeveloped lungs, and suffers from partial deletion of the second chromosome, a condition the doctor could find in only about 20 recorded cases of worldwide.
He has a feeding tube permanently attached to his stomach, and had a cleft palate which was surgically corrected.
Mrs Huijs said there would never be a cure for William's disabilities, which would not lessen with time, so all they could do was try to keep him from getting sick and suffering more lung damage.
Mr Huijs said having a "dry, clean, warm house" would help with William's lung issues. The house would also have easier access for a wheelchair, wider doorways and a wet-floor bathroom, among other features.
The Givealittle page showed 57 donors had given $3857 so far but the goal is $235,000.
William's parents said they had received a lot of help from the hospital but assistance was limited until William was older.
"We've been really lucky with friends and family," Mr Huijs said. "It's just amazing what they're doing."
The couple wanted to thank friends, family and the Whanganui Hospital, particularly the nurses.
Despite the health problems, they said William was an "easy" child.
Mr Huijs said he was "incredibly proud" of his son before he even came home from the hospital, because of what he had been through.
"He's an awesome kid."
Head to givealittle.co.nz/cause/william to donate to William's new home.