Ms Martelli said all of the team resonated with the cause, which allowed families of children with serious illnesses to have a holiday at the Ngongotaha lakeside retreat.
"It's so hard to see them struggling with all they have to go through. That's why the team get behind this."
Ms Martelli said auctioning off the no commission prize was unusual.
"We don't know what we are giving away. It's massive really. Hopefully people will see the benefit in it."
Supper Club organiser Linley Parry said Ray White Rotorua had always been "stunning" supporters of the charity.
She said it was part of the original team when looking for a property to set up the retreat.
Mrs Parry said it had been actively involved from then as "enormous supporters" of the retreat, not just financially but spending time greeting families who were staying.
The idea of auctioning off the "no commission" property sale was hatched after last year's Supper Club, Mrs Parry said.
"We are really, really excited about this auction item and can't wait to see how people receive it."
Mrs Parry said they had an amazing range of auction items for Wednesday's fundraiser, and she expected about 140 items would be up for grabs.
This year people can also bid online - even if they are not attending the sold-out event - and bidding has already started on some items.
To find out more and bid go to www.galabid.com/rsc2017.
