Calgary earned a sweep of New York on Tuesday when the other Flames' squad beat the Islanders 4-2 in Regina, Saskatchewan.
Michael Grabner gave New York a 1-0 lead just three minutes in, but Calgary took over in the second period with four straight goals. TJ Galiardi, Lance Bouma and Curtis Glencross also scored for the Flames.
Griffin Reinhart and Riley Wetmore had goals for the Islanders, who played their first two preseason games Tuesday.
Wideman scored his first of two goals at 7:39 on a shot from the blue line that deflected past goalie Kevin Poulin to make it 1-1. He netted his second during a 5-on-3 power play, beating Anders Nilsson, who replaced Poulin.
Galiardi added another power-play goal 48 seconds later.
Joey MacDonald played the whole game for Calgary and made 18 saves.
Poulin stopped 14 of 16, and Nilsson turned aside 11 of 13.