The accident happened just before 6 p.m. as the three were walking across 101st Avenue.
The car was heading north on 81st Street, made a left turn, and hit them.
The mother and her 2-year-old son and 5-year-old daughter were all rushed to Jamaica Hospital.
The 5-year-old girl is in extremely critical condition.
The mother and her son are in stable condition.
There is no criminality suspected.
Police say this looks like a terrible accident.
The 53-year-old woman that hit them stayed at the scene.