"We believe that if the community continues to get behind us, we'll hit $10,000 before the end of the weekend," he says.
The men have the support of 21 major sponsors so far, who have given money, clothing and shoes.
One sponsor has requested the pair walk around the lake in their underwear — which Ollie admits he's looking forward to.
"I'm definitely looking forward to this lap due to how free we will feel," Ollie says.
"I think I might pick Gerard some undies to wear on the day."
The men are fundraising for the families of 50-year-old Steve West, who has motor neuron disease, and 11-year-old Dayton Harding, who needs stem cell treatment to combat his autoimmune disease.
The men are hoping to attract a crowd of supporters at Lake Ngāroto over the weekend, with the public invited to join in on a loop around the lake on Saturday at 10am.
To make a donation, get in touch with Gerard on 027 505 4008 or Ollie on 027 290 9268 or donate to the bank account 12-3134-0093023-04.