Harkamaljit Singh, 34, doused the new car in petrol, struck a match and turned himself and the children into human fireballs outside his former wife's home in Manor Park, London, on 27 March this year.
Amarjit Kaur, 30, cried as she told Walthamstow Coroner's Court of her desperate attempts to save her seven-year-old daughter, Saran Kaur Ubhi, and her nine-year-old son, Simranjit Singh Ubhi.
Mr Singh, a rubber factory worker, from East Ham, had limited access to the children following the couple's divorce weeks earlier. He had collected them from the house for a couple of hours but Mrs Kaur became concerned when he did not return on time.
"I called the police and told them I thought he might have taken them to Europe and I thought he might hurt them.
"I went to see a friend and on the way back I recognised my husband's car and I saw my son in the passenger seat.
"He looked at me and I started to run up to the car. I noticed a strong smell of petrol. The car was going quite slowly and I saw liquid seeping out of the front passenger door.
"The car stopped outside my house. My son was looking at me. I was banging on the window. I looked down and there was petrol at my feet.
"I kept struggling with the door and my husband looked at me and all of a sudden, I saw him with a match and a match box and he struck the match."
Mrs Kaur dialled 999 and called the fire brigade, and then rushed out again to try and get her children out.
However, someone shouted: "Get back!" and police forced her back into the house. Later the police informed her that her children and former husband were dead.
Mr Singh's cousin, a solicitor, Baljit Ubhey, told the court that he had been upset by the breakdown of his marriage and by his wife allegedly having an affair.
The coroner, Dr Harold Price, recorded a verdict that Mr Singh killed himself and that the two children were unlawfully killed.