Tom Albrighton, from Birchmoor in Warwickshire is approaching the end of a daily half-mile walking challenge ahead of World Down Syndrome Day on March 21.
The money raised during his 21-day effort will go to Positive About Down Syndrome (PADS), an initiative which supported his mother Kelly, 31, after he was born.
Mrs Albrighton, a children’s mental health nurse, told the PA news agency: “The amount of hard work and extra effort it takes from him just to even walk half-a-mile is incredible and I’m hoping people can see that.
“He’s proved those paediatricians wrong right from day one, and for me that’s way more than I ever thought would happen.”
Mrs Albrighton said Tom has had 90-minute weekly sessions to help his physical development since he was nine months old.
It takes him “about an hour” to complete each half-mile walk.
She said: “It’s strengthening his muscles, his core, it’s tightening his ligaments, all of that takes time.
“It doesn’t happen overnight. A lot of it comes with age, physically getting bigger and stronger.
“He loves to be out and about. He’s a very determined little boy.”
Mrs Albrighton said she had “a really negative experience in how Tom was diagnosed” when he was born, citing “really negative language” and “lots of scary predictions”.
She added: “When we left hospital… we didn’t even have a leaflet about Down syndrome.”
She came across PADS, by charity Down syndrome UK, while searching for support online shortly afterwards.
PADS offers parents an insight into the lived experience of having a child with Down’s syndrome.
Its website reads: “Life is so much more than a diagnosis, there is a good deal to celebrate.”
PADS founder Nicola Enoch, 56, from Leamington Spa said: “In maternity care, the information provided is very medical, because it’s provided by medical practitioners.
“My experience is, what people really crave is the reality, the understanding of what everyday life is going to be like.”
Mrs Albrighton said: “If it hadn’t been for (Nicola) and the support we’ve found from her charities, I don’t know where we’d be right now.”
People with Down’s syndrome have an extra copy of chromosome 21.
Tom is one of many who are participating in PADS’ 21-day challenge to raise awareness ahead of World Down Syndrome Day on Sunday.
To find out more about Tom’s challenge, visit https://uk.virginmoneygiving.com/KellyAlbrighton.