He will be flown to New Jersey on September 18 and will receive the operation four days later.
The operation, selective percutaneous myofascial lengthening or SPML, would avoid further contractures (stiffness of muscles and tendons), and reduce the need for further surgeries. It involves small skin incisions, 2-3mm in length, to release tight bands of tendon.
After the operation James would receive therapy in New York for several days before flying to Croatia for another two-and-a-half-months of intensive therapy.
Mum Sonja Reid said she was both excited and nervous.
"Yes we've done amazingly well on the fundraising front, we never thought we'd actually get this far," she said.
It was decided James and his father would fly to America together for the first part of the trip and Mrs Reid would meet the pair in Croatia and take over James' care, she said
Mrs Reid said she had started telling her son he would be going on a plane trip to America without including the specifics of the trip yet.
"We are trying to make it exciting for him, an adventure and he is going to see a special doctor who will put some magic in his legs," she said.
The 10 weeks of therapy in Croatia, which would include three hours of therapy a day for five days a week, would be a gruelling experience for James, she said.
"He doesn't like doing anything physical at the best of times so it will be a real mental as well as physical challenge for everybody involved - it will be tough.
"But hopefully we will see some good gains out of it."
"We should see way more freedom of movement within him which will hopefully give his brain the opportunity to make new pathways, and move better."
Mrs Reid said the family had been humbled and overwhelmed at the community's support.
Can you help?
James' Givealittle page is still open and any more money donated would be used for further treatment for the little boy. To donate head to: https://givealittle.co.nz/cause/TeamJames
