Encephalitis is inflammation of the brain caused either by an infection or through the immune system attacking the brain and it causes Mostyn to thrash about with his arms and legs.
The family are now in the process of getting their house renovated ready for when Mostyn can make the final move back home.
Mrs Baigent said Mostyn's condition meant he was susceptible to coughs and colds. Their home was 40 years old and had very little insulation and so major alterations were needed to move him into his parent's larger room.
"He has no B cells and half his immune system is missing."
When he moves home he will need a number of medical machines with him and room for a carer to stay over night.
Financially the family have struggled as they have taken leave from their jobs to be with Mostyn in hospital. Apart from a $45 a week disability allowance, they didn't qualify for financial aid.
Their mortgage protection insurance was invalid as Mostyn was under 3.
So the Whangarei community has rallied and a dinner featuring All Black Richard Kahui will help raise money to allow the family to make the necessary home alterations and insulation.
Mrs Baigent said her coffee group had been supportive and was the driving force between the dinner on July 5.
The family had been overwhelmed by the support shown by local businesses which donated items for auction.
"At first we were kind of embarrassed about it but now we realise just how supportive everyone is."
One of the dinner organisers Marcela Thompson said some of the items for auction included a weekend package in Queenstown.
Mostyn's charity dinner is on July 5 at Horahora Rugby clubrooms, at 6pm. For tickets email Marcela on almostyn2013@gmail.com, or phone 0212876551/ 094372842.
