Friends launched a campaign to raise £250,000 and reached their target in 12 weeks, with Sarah admitting she thought “we’d never make it in a million years”.
The fundraiser has since been increased to £350,000 to help with ongoing costs, and more than £300,000 has been raised so far.
She added: “It’s absolutely incredible and there are not enough words in the world to thank people.”
Despite everything, Sarah described Teddy as a cheerful “social butterfly” who had remained positive throughout.
“His friends are learning how to jump in muddy puddles and do climbing frames and Teddy’s learning how to take blood pressures and use a stethoscope.”
Sarah said more focus, support and research was needed for childhood cancers and that funding was “harrowing” compared to adult cancers.
“We shouldn’t need to be raising all this money to fly the other side of the world for drugs,” she said.
“I just want Teddy’s story to be known so that the next person coming behind us doesn’t have to go through this excruciating journey that we have.”
The Welsh government said improving cancer care was a “top priority”, with a 10-year strategy focused on better prevention, diagnosis and treatment aimed at improving services and outcomes for patients of all ages.
It added that, through Health and Care Research Wales, external, there was funding for “early stage clinical trials for children and young people” through a partnership with Cancer Research UK.