When he made the promise in November last year, the 66-year-old had still been walking about 20km a week with his chemotherapy bag attached.
However, in February he had a seizure and required surgery because the cancer had spread to his brain.
"Up until then he was feeling quite good on chemo and could walk so was going to do it with me. And then he had his brain surgery and I said, 'Right, you are coming with me whether I push you in a wheelchair', and now he can't."
Without her father by her side, the 43-year-old will be walking with her own teenage sons, uncle, cousins and close girlfriends.
At the start of 2013, Mr Walsh left his job as a part-time cinema projectionist and moved to Orewa with his wife, Diane, to spend their retirement by the beach. Less than two months later, he was diagnosed with cancer.
Mrs McLeod said: "He always said, 'I don't want to be one of these people that leave it too late to retire and have my health be an issue', and unfortunately that's what happened."
The customer care manager admitted she was struggling to find the motivation to train as she dealt with the grief of losing her father.
"He always used to be ahead of me. He was a fast walker. But I sort of feel him pushing me along and it gives a lot of comfort. It will be emotional but I just feel really lucky because he was the most incredible, incredible man in the world. I'm just lucky to be doing it for someone so special."
On his last night at home before being moved to hospice, he also gave her his gold chain with a St Christopher charm she had given him 20 years earlier and which he never took off. She would also wear this in his memory.
The Walking Stars event will start on November 22 at twilight from Auckland Domain and money raised will go towards two cancer charities - the Cancer Society of New Zealand and Look Good Feel Better.
