"It was a family challenge that was brought up about July last year," Vercoe explained.
"You could put your name down for the 5km, 10km, half or full and I put my name down for the full."
The Waikato University student, who finished at Western Heights High School last year, said 15 out of her 22 family members were taking part on Saturday, across the various distances.
"We do little challenges here and there and we are a pretty competitive family, but this is our biggest event yet," she said.
Four members of her extended family will tackle the full marathon with her on Saturday, she said.
Vercoe said the entire family would be wearing matching fluoro-yellow shirts on the day and they would be hard to miss.
Meanwhile, the oldest competitor in the field is looking to do his 50th marathon.
"I've got no brains," Thorne said with a laugh.
"It's something I do, and do, and do."
The Whangarei man started doing marathons at age 64 - a late age to make your marathon debut - and will run his last this Saturday.
"This will be it. The machine's getting a bit worn out. It's getting slower and slower."
Wife Betty was relieved. "I get tired just watching him," she said.
Thorne joked he would be glad to see the back of the 42.2km run on Saturday as it was a long distance.
This will be the 22nd time Thorne has run the Rotorua event, which he believed was New Zealand's toughest marathon due to its hilly course.
A few family members will join him in the marathon, which he was chuffed about.
Asked his secret to being so fit at such an impressive age, Thorne said it was about eating well, not smoking, rarely drinking alcohol and training every day but Sunday.
He either runs, goes to the gym or water-jogs.
He also follows a special ritual; eating fish and chips the night before every race.
Thorne said he would keep running half marathons. He has run 93 of those and will aim for 100.
The oldest Rotorua runner taking part this weekend is Alan Lord, who is in his 80s. Additional reporting APN
