The youngsters were walking with their grandmother when they made the discovery outside the Boiling Springs Bank in Ridgewood on Thursday.
Police Sgt. Peter Bolten tells The Record newspaper the bills apparently were dropped, perhaps by someone who had just come out of the bank. Some of the cash was on a sewer grate while other bills had fallen through it.
Bolten says a large amount of money was recovered. Police are not saying how much because they expect the person who lost it would be able to say in order to claim it.
The children's parents asked police to withhold their names.