Carlita has done an ocean swim before, but the twins have done only a small ocean swim as part of a triathlon, so this will be a new experience for them.
The family are based in the small settlement of Waipapakauri Ramp, which has only about 50 houses and is 20km from Kaitaia.
Meanwhile, Dargaville accountant Kathryn de Bruin is hoping it will be third time lucky when she takes the plunge.
The 42-year-old is determined to overcome the seasickness that ruined her last attempt at completing the swim.
"The event prior to that two years ago, I had done all the hard yards for training and a fortnight before the event I got an infection in my ankle and ended up on crutches," she said.
"I was unable to do anything, let alone swim, which was totally devastating after all my hard work."
After much research and talking to others who have suffered seasickness, she will be wearing wristbands that put pressure on the underside of the wrist and will try chewing ginger before she takes the plunge with an expected crowd of 800 other swimmers.
"This is what works for people who swim the English Channel," said de Bruin.
"I am determined not to let the swell get to me again."
