"He might be in for a bit of a shock at just how few go. But that's what happens when you leave in disgrace," one source said.
Earthquake Recovery Minister Gerry Brownlee was informed of Mr Sutton's farewell plans on Tuesday.
However, he won't be attending today, a spokesman confirmed. "It's a departmental matter."
State Services Commissioner Iain Rennie - criticised for his handling of the Sutton saga - has also chosen to keep his distance.
"This is a private function for Cera staff who wish to attend," a spokeswoman for the State Services Commission (SSC) said.
The senior staff member who filed a formal complaint of sexual harassment against her boss last year has since returned to work after Mr Sutton's resignation in November.
It's understood that woman - who has remained anonymous throughout the scandal - has been working "as normal" but has decided to take a day off today.
"She's not a big fan [of the farewell] but she hasn't made a big deal of it," said one source.
"There are people in the [Cera] building who aren't happy that it's actually happening and there will be plenty who aren't attending.
"Something kind of had to be done, I suppose, but at least it's not a big hoo-hah. Those who love him will go."
Mr Sutton resigned after a seven-week SSC investigation found serious misconduct on his part following a complaint by a staff member about sexual harassment complaint.
The complaint was upheld, but was not serious enough to warrant dismissal.
A Cera spokeswoman said today's alcohol-free afternoon tea was an opportunity for staff to farewell Mr Sutton.
All Cera staff had been invited to attend but it was up to staff whether they attended, the spokeswoman said.
"The purpose of the afternoon tea is to recognise the service Roger has given to Cera and the recovery, and to respond to the wishes expressed by some staff to have an opportunity to farewell him.
"The matters which led to Roger's resignation will not be discussed at the function."
Mr Sutton's role as chief executive officially ends on January 31.
Former deputy State Services Commissioner and establishing Cera chief executive John Ombler has been acting chief executive of Cera since December 1.
He is due to speak at the afternoon tea.
It's understood that Mr Sutton has been warned not to use the event as a platform to again give his side of the harassment allegations.
Mr Sutton told RadioLive the farewell was an opportunity for him to "look a lot of people in the eye and say 'thank you' for working so hard and being so dedicated and supporting me through three and a half years of really hard work".
