They figure the band's crew noticed homemade T-shirts that dad Jamie Green had made especially for his kids' first time seeing a live U2 gig.
The concert took place July 8 at the Hippodrome. Mr. Green was there with his wife, Tara, and their children, seven-year-old Elena, Ethan, 10, and Brooklyn, 15. The concert had an attendance of 80,000 and the Greens paid for general admission tickets and were in an area where it was standing room only.
"We were way at the very back and once the concert started I had Elena on my shoulders. Jamie had Ethan on his shoulders," Ms Green said.
About three songs into the concert, a security person approached them and asked how many were in their party. Mr. and Ms Green apparently thought they were going to get scolded for obstructing the views of the people behind them. Instead the staffer said "come with me."
The Greens were led out of general admission and given five tickets to enter Section 122, a hop, skip and jump from where Bono and the gang were belting out the tunes.
"It was one of the closest sections to the stage," Ms Green recalled.
"It was pretty exciting when he gave us the tickets."
Her husband, a lifelong U2 fan, expressed his excitement to the Montreal Gazette. "We were so close I could see [Bono] sweating," an elated Mr. Green told the Quebec-based newspaper.
"It brought tears to my eyes. It was so great for the kids. People around us were patting them on the back saying, 'Good for you.'"
The Montreal Gazette said the Green children couldn't see very well because they were at the back behind a control booth. The band's crew took notice when the couple hoisted the two youngest kids, who were wearing shirts that read "My 1st U2 concert," on their shoulders, the paper said.
The family originally planned to attend the Montreal concert in 2010 but that was shelved when the lead singer had back surgery. "We had our tickets for two years," Ms Green said.
The Greens will be watching U2 live again in the coming weeks. They'll be in Moncton to see the band at the end of the month. She said nearly every vacation they've taken together at some point means a U2 concert. But she doesn't mind.
"He gets to go to U2 and I get to go somewhere different," she said with a laugh.