The incident took place around 1.30 pm when a number of devotees were going for a religious event and the driver of the tractor-trolley, in which they were travelling, lost control of the vehicle on a steep road at Lalsot.
The two children, who are yet to be identified, were killed on the spot, while 15 others were injured. The driver, however, was not hurt, police said.
The injured were rushed to nearby government hospitals in Dausa, police said, adding that the bodies of the deceased were sent for post mortem.