"There are quite a few New Zealand children going through this so I have been in touch with some of the mothers and we are hoping to start a foundation that would raise funds towards research to find a cure.
"There are lots of similar foundations in the US, UK and Australia but none that we are aware of here in New Zealand, and we really think it would be great if we can work together and help increase awareness of DIPG and fund some research to help find a cure."
Preparation for the event has involved plenty of walking on their beef and sheep farm at Sherenden (just west of Hastings).
"I do a lot of walking anyway, mainly around our farm, so I am used to walking, but I will ease into things with the half in Hawke's Bay. I have been walking five times a week for an hour to an hour and a half, I am hoping that prepares me well enough but I will step up before the event with some longer distances."
"Life is too short to put things off, it is always something I wanted to do but never got around to," Heidi said.
Heidi won't be doing it alone, with about four friends joining her in either the 10km or half marathon, while her husband, Michael, and their 8-year-old daughter, Charlotte, will be supporting her on the day.
She plans to attempt the Queenstown Marathon later in the year, or return for the full marathon in Hawke's Bay next year.
"This has taught me that you have to make the most of any and all opportunities that come your way and don't put things off. Marcus taught us to make the most of every day and every opportunity. That's why I'm entering this event."
The Air New Zealand Hawke's Bay International Marathon will be held in Hawke's Bay on May 13.
For more information visit: www.hawkesbaymarathon.co.nz