Matthew Tvrdon, 32, drove his van on an eight-mile 'journey of mayhem' lasting 30 minutes on 19 October 2012.
Karina Menzies, 31, died when she was hit by the van near Ely fire station in Cardiff. Her 26-year-old sister Samantha is now bringing up the traumatised children.
Tvrdon, who has paranoid schizophrenia, has admitted manslaughter on the grounds of diminished responsibility at Cardiff Crown Court.
He has also admitted seven counts of attempted murder and other charges including three counts of grievous bodily harm with intent.
The court heard he knocked people over like 'skittles' as he targeted adults and children at five separate locations in the west of Cardiff. He is due to be sentenced today.
Yesterday, Karina's family told how she sacrificed her life for her two children - by using her body to shield them from the white van maniac. Karina was holding her daughter's hands as they walked home from school when they heard the roar of Tvrdon's van behind them.
Devastated sister Samantha said: "Karina died saving her own children from Matthew Tvrdon.
"They remember how she pushed them to safety but was killed there instead of saving herself.
"The girls were holding their mum's hands on the way home when they saw her killed right in front of them.
"How will they ever get that image out of their head?
"Her daughters still cry for her and all I can do is cuddle them and tell them how much she loved them.
"Our family has been destroyed because of what Matthew Tvrdon did that day.
"We are very lucky we didn't lose Ellie and Tiana as well.
"The two little girls have recovered physically but still bear the mental scars of seeing their mum die in front of their eyes."
The girls are being brought up by Karina's sister Samantha just 10 minutes walk away from the scene of the fatal hit-and-run.
Samantha said: "There are no words for what they have seen and been through.
"Karina was the most intelligent and funny person I have ever known. We all miss her so much - but nobody more than her children."
Karina's eldest daughter, Sophie, who has a degenerative muscle disease, was on a holiday for disabled children in Disneyworld, Florida, at the time of the crash in October last year. The family waited until she came home four days later to break the tragic news her mum had gone.
Samantha said: "She was hysterical and screamed: "Where am I going to go?" - she begged not to be put into care.
"But by then I had already decided to bring all three girls up as my own.
"It is what Karina would have wanted - I love the girls and I'm doing my very best to care for them and soothe their nightmares.
"Nothing will replace Karina. They miss her smile, her hugs, her laughter."
The Family Court has made qualified nursery nurse Samantha the girls' legal guardian.
Although she has no children of her own Samantha is doing her best to create a big happy family with her partner Lee, 40, and his three children, aged 11 to 16.
Samantha said: "Life is still a complete rollercoaster. One day I think the girls are coping quite well, the next it's clear to everyone they aren't.
"The girls still have so much grieving to do. They talk about their mum all the time and we have pictures of her everywhere.
"If they cry for her I cuddle them and tell them how much she loved them.
"At least my nieces can feel safe knowing their mummy's killer is behind bars and he can never hurt them again.
"I hope I can be as good a mum to her as she was."