Nigel Cass, NZ Rugby's general manager of planning and operations, said the organisation was pleased the announcement would be made at Parliament.
"[This is] a place which represents all of New Zealand, and a venue which has hosted many sporting events and teams in the past, including the All Blacks."
Labour's sport and recreation spokesman, Trevor Mallard, said he had been invited and would attend the event, and it was up to NZ Rugby to decide how to run the announcement.
Dr Coleman said many different organisations used Parliament for events.
"NZ Rugby approached my office, as Sport and Recreation Minister I was happy to facilitate. The All Blacks are New Zealand's team, and the Rugby World Cup is an important event for many Kiwis."
While his predecessor Helen Clark was known for her love of rugby league, Mr Key has forged a particularly close relationship with NZ Rugby during his time in power and is a regular visitor to the All Blacks' changing room after matches.
Mr Key and his son Max posed with players for dressing room photographs after this month's Bledisloe Cup match at Eden Park.