Friends of Otimai described the process as being untrue to the values that Guiding stands for and claim losing the Otimai camp, in West Auckland, could rob young members of valuable life experiences.
But GirlGuiding NZ says the land has to be sold to help secure the movement's long-term future.
Ashes of old girls as well as their relatives are scattered at the site, and there are fears these could be disturbed.
"We are concerned that there is no requirement for the purchaser to have any regard for the cultural, spiritual or historical significance of the site," said Hucke.
The small but vocal group against the sale of Otimai believed the board valued money more than history and tradition, and had made up their minds to sell long before officially announcing it - something the organisation's chief executive strongly denied when the Herald spoke to her in August.
Maintenance issues and financial viability were brought into question after the property was found to be running at a loss of nearly $200,000 between 2009 and 2015.
GirlGuiding New Zealand boss Susan Coleman said a loss of that size was simply not sustainable for a charitable organisation.
Context box:
Otimai, meaning "welcome, come and stay," is for many Guiding members the symbolic home for Guides in New Zealand.
It was the first Guiding centre in the country.
The 3ha property was gifted by the movement's first Chief Commissioner R. W. Wilson and her family to the Girl Guiding movement in 1927.
Its lodge sleeps 40 people and the grounds include a fairy ring, manager's cottage, hand built chapel and a large camping area.
Address: 1 Kauri Loop Rd, Oratia, Auckland.
It will be put up for tender on the 8th of September, closing on the 6th of October.