"It's always easier to play when you have a lead, especially when it's 3-0, 4-0, 5-0," said Reimer, whose wife flew in from Vancouver earlier Saturday. "You know there's not as much pressure on you so you can relax a little more."
Maple Leafs coach Ron Wilson said he decided two days earlier to start Reimer, whose parents and sister were also in the crowd.
"He knew about it," Wilson said. "I certainly wasn't going to share that with the piranhas in our media that would maybe upset him a little bit, and he was able to calmly go about his business and be ready for the game."
"We had a tough couple of losses in our last two games," Bozak said. "Both games we thought we could have won so it was big for us to come out here and get a lead, and then not sit back but build on that lead."
Sergei Gonchar scored a power-play goal later in the second for Ottawa, which lost its third in a row (0-2-1).
"It was absolutely frustrating," Senators left wing Nick Foligno said. "We don't know for what reason the game got so out of hand but it's tough to deal with, obviously."
Brian Elliott stopped four of seven shots before he was replaced 16:10 into the game. Mike Brodeur made 12 saves in relief.
MacArthur opened the scoring at 1:57. He spun around to drive a shot past Elliott for his 10th goal.
Kessel stripped the puck off defenseman Erik Karlsson and passed it to Crabb to begin the play that led to Toronto's second goal.
Crabb drove into the Senators zone and passed the puck back to Bozak, who fired a shot past Elliott from the slot at 12:24.
Bozak struck again at 15:21, combining with his linemates again to make it 3-0.
Boyce, who got an assist in his season debut on Thursday, made it 4-0 when he beat Brodeur 3:18 into the second for his first goal.
Schenn's second of the season made it 5-0 at 5:46.
Reimer made 11 saves in the first, 10 in the second - when he was beaten for Gonchar's fifth goal - and 11 more in the third. He stopped each of the four shots he faced in his debut on Dec. 20, when he relieved Jonas Gustavsson in Toronto's 6-3 loss to Atlanta.
NOTES: Maple Leafs C John Mitchell was a healthy scratch. ... Senators LW Jarkko Ruutu was left out of the lineup for a second night in a row.