Fully vaccinated travellers from visa-waiver countries will be able to enter the country from 11.59pm on May 1.
Nash announced the South Island fund this morning for five regions: Fiordland, Queenstown and Wanaka, Kaikōura, the Westland glacier region, and Mackenzie District-Aoraki Mt Cook.
Applications to the fund will formally open on April 1.
He said tourism operators in these places worked hard to stay connected with the travel, culture, hospitality and recreation sectors.
But some still had to slash opening hours or greatly scale back operations during the pandemic, Nash said.
Grants could be used to refresh facilities or marketing, train and hire new staff, or source new stock ahead for opening, he said.
"It will take time and money, and is exactly what the tourism kick-start fund is for."
Details of eligibility criteria and contact details relevant to the scheme will be on the tourism recovery section of the MBIE website, he said.
Meanwhile, Auckland Business Chamber chief executive Michael Barnett's message to Australians was simple: "Come on over."
And Heart of the City chief executive Viv Beck welcomed the reopening news but said more urgent help was required, and more workers needed to head back into CBD offices.
"This is news we have been desperately waiting for, as this is now the toughest time of the entire pandemic for many."
That plan was previously for vaccinated travellers from Australia and visa-waiver countries to come in by July, and those from the rest of the world from October.
Hospitality New Zealand chief executive Julie White said the earlier border opening would save many businesses, and now it was time to get rid of vaccine passes.
"It's sensible and safe to open the border at this time, with our high vaccine rate and Omicron in the community meaning there is no additional risk to our communities," she said.
"Opening before winter will be a game changer for so many businesses in the hardest-hit tourism regions, such as the southern ski resorts."
Air New Zealand chief executive Greg Foran welcomed the travel dates announcement.
"It's no secret the past two years have been extremely turbulent for people. There's a real buzz today," he said.
"New Zealand holds a special place in many people's hearts. Whether they're a Kiwi or visitor, touching down on New Zealand soil will be a moment to remember.''
Hotel operators Accor said the border announcement was positive news after two years of pain and sacrifice.
But Accor's Gillian Millar said the Government should move swiftly on reviewing the current Covid-19 protection frameworks such as the traffic light system.
"We urgently need a clear pathway at least to orange level of the protection framework to assist with delivering a quality guest experience for our domestic and international visitors," Millar added.
Dr David Welch, a University of Auckland computational evolution expert, said easing border restrictions meant new major virus variants could infiltrate New Zealand quickly.
"We will need to increase and improve our local surveillance efforts, including genomic surveillance of variants circulating in the community."
Covid-19 modeller professor Michael Plank said the Government needed a variety of sustainable measures to monitor Covid-19 variants coming in.
The two key dates announced yesterday did not provide any certainty for people outside visa-waiver countries.
For people in those nations, the major issue was how to process new visas in a timely way, Ardern said.
National's tourism spokesman Todd McClay said depriving these tourists of a visit because visas could not be processed was "a new level of Government incompetence".