In the days leading up to the marathon - which will take runners through the streets of the Lebanese capital - the Kiwi team will visit refugee camps on the border to meet some of the people they are raising money for.
Smalley said this would be a "confronting" experience for all involved. "Some of the families and the children have experienced huge trauma and their stories of survival are upsetting."
In three years working with World Vision, Smalley has met Syrian and Iraqi refugees in Lebanon, Jordan and Iraqi Kurdistan.
"It's not easy. Some of their stories of what they've seen and what they've fled are horrifying," she said.
Having already run two half-marathons, but never a full one, she has no idea what to expect.
But what better place to find out than Beirut, Smalley said, one of her favourite cities on earth.
New Zealand's response to the Forgotten Millions campaign this year was "truly incredible", she said, "but there are still millions of people who need help".
She is also hosting a Forgotten Millions gala dinner at the SkyCity Grand in October as a fundraiser for the marathon. Tickets, which cost $295, are now on sale.
If you are interested in running the Beirut Marathon, email gaz@getrunning.co.nz, or visit getrunning.co.nz.