"They hatched the plan and this is great to see this recognition - it is the first time this sort of service has been staged and I am proud to be part of it," Mr Grant said.
It will tie in to a weekend of military events around the region and across the country centred around Armistice Day, November 11.
It was on November 11 in 1918 that WWI was officially brought to an end.
As part of the service wreaths will be laid along with the lighting of a Remembrance Candle.
Mr Grant said it would likely be an emotional day "in many ways".
He served as a lieutenant with 1NZATTV (1st New Zealand Army Training Team Vietnam) in 1970 and 1971 and said preparing his speech had been challenging.
"It is one of the hardest addresses I have had to do," he said.
"Part of it is because I am a Vietnam veteran and in a way I'm not sure what to say - there were a lot of issues we had to deal with when we got back because we were not really welcomed home."
He said he and his comrades went away with the same resolve and ideals as those who had served in previous wars and thought they would return to a grateful country.
"But it was not."
Mr Grant said while protesters vented their anger against the government, many also personally went for the returned soldiers and their families.
He heard of families being rung and abused in the middle of the night after protesters discovered a son or husband was serving in Vietnam.
"A lot of people returned home with psychological injuries and families were also very much a casualty of war as well.
"All those who served over there had some level of psychological injury and of course the wives and families had to live with that too - so they also suffered."
Mr Grant would strongly make that point in his address.
Like other veterans he had been heartened by a change in people's attitudes to Vietnam service personnel, who all volunteered for service there, over recent years.
"We left some good boys behind there when we left to come home," he said, adding that many were still buried in Commonwealth War Graves in Malaya.
There were, however, governmental moves afoot to repatriate those bodies to New Zealand. "So they will finally come home."
Father Bill Chapman, who served in the Royal New Zealand Navy between 1961 and 1970 as a leading hand, said he had always enjoyed a close association with "all the boys" who had served in Vietnam while carrying out his duties as padre.
While not directly involved in the war, he was aboard HMNZS Blackpool in 1966 and 1967 "off the coast" when it was part of this country's involvement with the South East Asia Treaty Organisation (SEATO).
About three months ago he had been asked to do a service in Hastings as it was the 50th anniversary of the Battle of Long Tan.
"I started thinking about that - it has been 50 years since we sent troops to Vietnam, so I approached Potene and pointed out we had our Remembrance Sunday Service coming up in November."
They talked about devoting the annual service to a remembrance for those who served in Vietnam, and Father Bill broached it with the parish.
Mr Lima, as representative for the local veterans, met with the parish and the result delighted Father Bill.
"They were 100 per cent behind it."
Through his general padre work he had got to know many of the Vietnam boys and said he wanted to do what he could to right some of the wrongs which had been inflicted on them.
He agreed with Mr Grant that the anger of protesters against the war should have been directed solely at the government ministers of the day who declared New Zealand military involvement and not those who went to serve their country.
"They felt betrayed by the government, some RSAs and some felt betrayed by the church as a lot of church leaders had been in the protest movements."
Between 1963 and 1975 more than 3000 New Zealand military and civilian personnel served in Vietnam, although the first combat unit did not arrive until 1965.
Up until Prime Minister Keith Holyoake announced there would be a Kiwi combat unit heading there to join with US troops, New Zealand's involvement had been one of humanitarian aid, development assistance and civilian surgical teams.
At the peak of involvement in 1968 the New Zealand military force numbered 548.
By the end of New Zealand's involvement 37 had died on active service and 187 were wounded.
Two civilians serving with surgical and Red Cross teams also lost their lives there.
"We felt it was time we had to do something for our Vietnam veterans," Father Bill said.
"This will be their day."
● Remembrance Sunday - Remembering Our Vietnam Veterans, Sunday, November 12 at 11am, at St George's Memorial Chapel, Matapiro Rd, Crownthorpe.