"This is the first addition of a memorial to the site since 1964," Mr Mikaere said.
A breakfast will be held at St Thomas Aquinas College after the blessing, then the group will return to Te Ranga for a powhiri to welcome the dignitaries.
Afterwards, haka and waiata specially composed for the occasion will be performed.
Events next move on to a service held by Army padres, then back to Aquinas for lunch.
"It's a tragic commemoration because ... Tauranga Maori lost a whole generation of their leaders," Mr Mikaere said.
"One hundred and eight were killed there, then another 15 died at the hospital afterwards. Most of the people who died were bayonetted, which shows they were really unready to fight."
Work was being done to beautify the site with planting programmes planned for a period of about five years, depending on funding, so the site would become more of an environmental reserve.
Mr Mikaere asked traffic travelling around the Pyes Pa/Joyce Rd intersection towards Aquinas College to be wary of pedestrians.
A Western Bay of Plenty District Council spokeswoman said the council had assisted with ecological restoration of the site. Mayor Ross Paterson will be at the commemoration.
The commemorations will be open to the public.