"Let us pray for her and the baby boy she dreamed of, with her, in eternity, in her good care," Kelly said.
Sanz died on Aug. 14; her son, who was two months premature, died Friday.
During the two-hour service, Sanz was remembered as a dedicated worker and a loving wife who had donated a kidney to her husband, Rafael, shortly before their wedding four years ago.
Sanz was crossing a Bronx street on her lunch break when she was struck. The impact sent her flying into the path of a yellow school bus, pinning her underbeneath. About 30 bystanders rushed to hoist the 5-ton bus from her body in a rescue the mayor said "lifted the spirits of our entire city."
At the service, Bloomberg said Sanz was known among her colleagues for her "joyful laugh."
"When her fellow traffic agents came back from a stressful day on the job, they could always count on Donnette to lighten their mood with a joke or a funny comment," he said.
Bloomberg said the Jamaican native came to New York like so many others seeking opportunity.
"She grew up on an island know for its beauty and serenity and she carried that with her even as she walked the streets of New York City," he said.
One poignant moment of the service at Community Protestant Church came when a saxophone player delivered a jazzy but haunting rendition of "Danny Boy," the Irish standard that is often played on bagpipes at Police Department funerals.
Donnette Sanz had been a civilian member of the NYPD for two years, a job that required her to direct vehicles, write parking tickets and operate tow trucks. Unlike officers, traffic agents do not carry weapons.
Her commanding officer, Myrna Baxton, said Sanz was "focused and conscientious" at work and was "ecstatically happy" as she looked forward to the birth of her first child.
Sanz's grieving husband did not speak at the funeral.
The van driver, Walter Walker, 72, faces charges of criminally negligent homicide and aggravated unlicensed operation of a motor vehicle. A spokesman for the Bronx district attorney said Friday that prosecutors would wait for the medical examiner to determine the infant's cause of death before deciding whether Walker would face additional charges.
Walker's lawyer, Michael Torres, said his client had not entered a plea.
Walker has a long history of driving offenses and arrests dating to the 1980s; police have said he had his license suspended 20 times. In a court filing, police said the brakes on Walker's van had deteriorated so badly it was unsafe to drive. Walker has said he tried to avoid hitting Sanz but was unable to stop.
Burial was at Kensico Cemetery in Valhalla.
