The victims, aged 16 and 19, were walking together in the Massapequa Preserve at Lakeview and Boston avenues at 6:50 p.m. when they were approached by two suspects, police said.
One of the suspects, Aidan Boyle, 17, of Amityville, showed the victims a three-inch gravity knife and demanded that the 16-year-old victim give him his property, police said. The victim gave the suspect a black knapsack that contained a credit card and keys.
The other suspect, Boden Woelk, 20, also of Amityville, threatened to use physical force against the 19-year-old victim, who gave the suspect $10.
No one was reported injured.
Boyle and Woelk were charged with two counts of first-degree robbery, two counts of second-degree robbery. Boyle was also charged with fourth-degree criminal possession of a weapon and fourth-degree criminal possession of stolen property.
The two were scheduled to be arraigned on Sunday at First District Court in Hempstead.