Cooper and Geordie had moved to Whanganui to be with their mum, Kim Ostern, just four days before the accident, she said.
"Kim moved to Whanganui last year to get out of the rat race. The boys stayed with their father, Roger, in Tauranga, but they decided they'd like to move to Whanganui."
Mrs Steedman said Cooper was about to start a training course.
She has started a Givealittle page to help the family with the cost of travelling to the South Island to be with Cooper, and other expenses. The page can be found at here.
"It's a hideous time for the family. Kim has a good job here, but she doesn't know when she'll be able to go back to work. They've been told that if Cooper survives he'll be in hospital for at least six months. The family knows no-one in Christchurch and they have very little support there."
Mrs Steedman said she felt helpless and wanted to do something that could positively impact her friends.
The page was set up on Friday and nearly $2000 has already been pledged.
Ms Ostern said she was very grateful for the love and support of the Whanganui community.
She said her son had an "absolute passion for life".
"He absolutely thinks outside the square. He loves his friends and his brother. He loves fishing with his dad, snowboarding, climbing trees."
Mrs Steedman said Cooper had always been "full of beans" and everyone was hoping that his natural zest for life would pull him through this ordeal.