Mr Austin's great-grandfather, Rodney Rushington Taylor, from Maungaturoto, served four-and-a-half years as a trooper in the Auckland division of the Mounted Rifles, during the Gallipoli campaign in the Dardanelles, and later in Malta, and Suez in Egypt.
He was honourably discharged from the army with recurring illness, to recuperate in England.
While Rodney Taylor survived to age 79, his son (Shane Austin's great-uncle) Flight Sergeant Lawrence Taylor was missing, presumed killed, in World War II.
"To imagine what he [Rodney] went through in the war, and then losing his own son in World War II ... it's pretty special to be there," Mr Austin said.
He expects the Gallipoli service to be a huge occasion, and is picking the Last Post to be the moment he will feel the most emotional.
"Even though you can go to Anzac services locally, I would go less often than I ought," he said.
"[But] the 100th anniversary is a once in a lifetime opportunity."
Mr Austin expects the whole Gallipoli experience will be unlike any other holiday, particularly given the historical and personal significance.
"I haven't been [to Gallipoli] before, but you have to stay out overnight in potentially 0 degrees. It's nothing like what my great-grandfather experienced, but it'll be emotional to be in the same place."
He entered the ballot about 18 months ago, not expecting to be successful, but was thrilled when the good news arrived several months ago.
"When I was reading the letter, I was fully expecting it to say 'We regret to inform you ... ' but then I thought 'Hang on a minute, it says 'We are pleased to announce ... '."
He wanted to take his great-grandfather's medals with him to Gallipoli, but his great-uncle who has possession of them (himself a WWII veteran) didn't want to let them out of his sight.
Mr Austin's two girls, aged five and three, don't yet understand the context of their parents' trip, but they hope the girls will learn more about their great-great-grandfather in the future, and hopefully visit Gallipoli for themselves one day.