Birmingham Crown Court was told that Wayne Payne was travelling at 61mph when he hit Cameron Ward, who was being pushed on his bike by his father John Ward.
The crash happened in Erdington, Birmingham, as the schoolboy's family returned from an Easter party. Cameron's bike was being pushed by Mr Ward as the pair, his partner Katie Lawrence and their three-week-old baby headed towards a bus stop.
Howard Searle, prosecuting, said Cameron was fatally injured as he crossed the road with his dad on April 1 last year.
Mr Ward saw the headlights of a Vauxhall Vectra, being driven by Payne, in the distance before he stepped into the highway, the court heard.
Mr Searle said: "Mr Ward thought he had plenty of time to cross.
"As he got to the middle of the road he heard the roar of a car engine and realised the car was much closer to him.
"It was this defendant driving well in excess of the speed limit.
"He froze on the spot. The car being driven by Payne did not brake at all but drove into the bicycle. It hit the rear. Cameron was flung into the air and his father was injured as well."
Payne, 31, has denied causing death by dangerous driving. Mr Searle said the defendant lost control of the Vectra and it continued for 50 metres down the street before colliding with a parked car.
Police and paramedics were called to the scene but could not save Cameron.
Mr Searle said an accident investigator later calculated that Payne had been travelling at 61mph shortly before the collision.
He said the defendant, who later claimed he had tried to swerve, had admitted careless driving.
Mr Ward, 37, said he had seen the lights of a vehicle about 200 metres away and he had gone out into the road between two parked cars.
He said: "I thought it was safe to cross the road. It happened very quickly. It was over in seconds.
"I don't know how I got up but I did. I knew he was dead. I wanted to disappear. Cameron was my life and I had lost him."
The trial continues.