Jamie Leek of Clifton, Nottingham died in Zante in June 2012 when he was hit by motorcyclist Spiridon Koklas.
A Greek appeal court has upheld his sentence of four years and 10 months but suspended it for three years.
Jamie's mother Lydia said the family "feel cheated of justice".
"We are mortified by this and at a loss for words. We have to accept it is probably the end of the line in legal terms," she said.
Jamie and his family were on holiday in the resort of Kalamaki to celebrate his parent's 10th anniversary when he was hit crossing the road with his father.
More updates from across the East Midlands
The day he died was his ninth birthday.
Mr Leek suffered a broken arm in the accident but Jamie died later in hospital.
Koklas was convicted of involuntary homicide and involuntary bodily harm in 2015, but had appealed his sentence. He was not in court for the appeal hearing.
After a previous hearing, Mrs Leek said the rider "didn't show any remorse to us at all. He didn't show he was sorry one bit".
The family have been supported by Nottingham South MP Lilian Greenwood, who has asked two prime ministers  - David Cameron and Theresa May to help raise the issue.
Both promised the MP they would help the family by contacting the Greek authorities.
Ms Greenwood said: "I am really shocked, angry and upset that despite the long quest for justice for their son Jamie it has resulted in what feels like a totally inadequate sentence.
"It has taken several years to get to this stage and then for the sentence to be suspended feels like a complete kick in the teeth."
The family of a nine-year-old British boy who died after being hit by a motorcyclist in Greece five years ago are "mortified" that the driver will not be jailed.