Tania Clarence, 42, is to appear in custody at Wimbledon Magistrates' Court in south west London today.
Post-mortem examinations are being carried out at Great Ormond Street Hospital on the children, who have been named as three-year-old twins Ben and Max, and four-year-old Olivia.
They were found dead at their home in New Malden, south west London, on Tuesday night.
It is reported that the children were suffering from Spinal Muscular Atrophy (SMA) - a life-limiting genetic illness.
Their father, Gary, who works as a director at City bank Investec, was said to be away in the family's native South Africa with the couple's eight-year-old daughter when the deaths occurred.
Family spokesman Lloyd Marshall said that Mr Clarence was in "absolute shock" at the tragedy.
He said that after the four-year-old was diagnosed with the condition it was "50-50" as to whether the twins would also have it.
"Unfortunately, they did as well," he said.
He added: "Gary is in absolutely a state of shock - the whole family is. He never would have left the UK if he'd known (his wife) would be left really battling.
"Most of the family are on their way to the UK."