Prime Minister Jacinda Ardern is expected to make an appearance at the Te Waru o Noema centenary celebrations at Rātana Pā next month.
About 25,000 people are likely to come to the settlement near Whanganui. Accommodation providers in town expect to be fully booked.
The crowds will celebrate the day 100 years ago when prophet Tahupotiki Wiremu Ratana saw the vision that began the Ratana movement. Followers all over New Zealand have been waiting for the centenary.
There will be MPs, iwi and church leaders and possibly the Governor-General there for the big day, November 8.
Prime Minister Jacinda Ardern is also expected to be there for the church service on November 8.
Gaylene Nepia is co-ordinating the huge event, with former police officer and current Conservation Department strategic Māori relationships manager Te Rangi Maniapoto as security director. He said his biggest worry was that campaigners might seize the moment to get media attention - and anti-1080 groups were the most likely to try.
In Palmerston North an anti-1080 group threatened to put the poison baits in the city's Freyberg Pool.
"Although it's a religious celebration, it becomes a national focal point for media. People may try to use that to leverage off and get the national media attention," he said.
Church secretary Piri Rurawhe said people would not be allowed to used the occasion to push their own kaupapa (causes).
Alcohol is banned from the pā, and no gang patches will be allowed either.
The day is the most important in the church calendar, he said.
"It's 100 years since the vision of the Holy Spirit to TW Ratana. People of all faiths will be there. Every church here in one place and one time is quite a momentous achievement for New Zealand."
On November 7 visitors will be welcomed, starting with Ratana faithful, then iwi, then churches, then political parties at 3pm. There will be entertainment in the evening.
November 8 has a church service and plaque unveiling, followed by a hakari (feast) and more entertainment. November 8-9 will also see the rangatahi (youth) programmes, another evening of entertainment and an archive exhibition.
Massive preparations are underway at the pā, where there will be five marquees, disabled toilets, a medical centre, space for camping and caravans and huge car parks.