Other footage shows a woman wearing a burka hugging the girls, dressed in coats and woolly hats, before they leave.
Syrian journalists are reporting the adults in the footage are the parents of the children.
The woman is asked why she is sending her daughters to jihad even though they are so young.
"No one is young when it comes to jihad as every Muslim is supposed to participate in jihad," she replies.
The blast that rocked a police station in southeast Damascus last week was caused by the 7-year-old who was carrying a belt of explosives.
The explosion in the bustling Midan neighbourhood of the Syrian capital wounded three police officers, said the Al-Watan daily, which is close to the government.
"A 7-year-old girl entered the police station, carrying a belt that was detonated from afar," the paper posted on its Facebook page.
A police source told Al-Watan that she had appeared lost and asked to use the bathroom when the explosives went off.
More than 310,000 people have died since Syria's conflict broke out in 2011.