Chuck Kobasew, Dennis Wideman and Phil Kessel also scored for the Bruins.
Nate Thompson and Richard Park scored for the Islanders.
Manny Fernandez stopped 22 shots for Boston and is 6-0-1 after losing his first start.
With the score tied 1-all, Ryder stole Brendan Witt's attempted clearing pass at the right circle and beat partially screened goaltender Joey MacDonald with a wrister over his left shoulder 15:16 into the second period. Krejci had positioned himself in front of MacDonald.
It was just the second goal in 13 games and fourth overall for Ryder, signed as a free agent during the offseason.
About a half minute after Fernandez stopped Bill Guerin with a sprawling stop on a clean breakaway, Wheeler one-timed Krejci's cross-ice pass past MacDonald to make it 3-1.
On the ensuing shift, Wheeler poked the puck ahead to Krejci along the left boards. Krejci cut around a defenseman and slipped a shot inside the near post.
Wideman made it 5-1 just 2:12 later, and the Islanders replaced MacDonald with Peter Mannino.
Ryder's second of the game came on a power play with just under five minutes left.
New York jumped ahead 1:46 into the game on its first shot on goal, when former Bruin Thompson fired a shot from the left wing that caromed in off the far post.
The Bruins tied it when Kobasew banged home a rebound from the edge of the crease 3:28 into the second.
Wideman hit the crossbar with a slap shot from the right point about two minutes before Boston grabbed the lead.
Wheeler had a crowd-pleasing move midway into the second when he backhanded a pass between his legs to himself and shifted around Islanders defenseman Mark Streit before being stopped by MacDonald.
The Bruins, looking to join the shopping craze know as "Black Friday," unveiled their new black third jersey for the game and took the ice to AC/DC's song "Back in Black" for the first two periods. They also gave out black T-shirts to the first 10,000 fans, attempting a "Blackout."
Notes: The Bruins held a moment of silence for former player and coach Armond "Bep" Guidolin, who died earlier this week. He was 82. ... Islanders RW Tim Jackman went to the locker room late in the opening period after being hit into the boards by Boston's Milan Lucic, but he returned for the second. ... The Bruins reassigned D Matt Lashoff to the team's AHL affiliate in Providence on Thursday. ... It was the opener of a two-sport, day-night doubleheader. The Celtics were to play Philadelphia at night. ... Guerin had a seven-game point streak snapped.