Mrs Marris and husband Clint's eldest daughter Belle had a congenital heart disease and was stillborn about 8-1/2 years ago.
So Mrs Marris told Ruby they could get a small block of Toblerone and do that if she wanted too, but suggested using the large block to make a donation to charity.
"Heart Kids would be the obvious choice," she said.
So an idea to raffle off the block and donate the funds to charity was created. On February 15, the day after Heart Kids Day, she made on a post on Facebook, including a video of 7-year-old Jaedyn and Ruby, and explained what they were doing.
Mrs Marris said despite never meeting her sister, Ruby has a special connection with Belle.
She said it's hard to explain, but Ruby talks about her a lot and often wants to include Belle.
The family always let helium balloons off on Belle's birthday in August.
Tickets are $5 each for the block of chocolate, but people can also make a donation if they like. So far $860 has been raised.
Mrs Marris said the family have been blown away with the response.
They plan to get someone 'official' such as a police officer to draw the raffle, and are looking at doing that at the end of this week, but are yet to confirm exactly when.
Jaedyn and Ruby will present the cheque to Heart Kids in Auckland and will get a tour to see how Heart Kids helps children with heart conditions.
Mrs Marris said the whole thing has been a cool learning curve for the siblings.
"They've gotten out of it just as much as they've given, which is cool."
Mrs Marris has a bank account specifically for this cause. To buy a ticket, transfer the money to 12-3099-0553003-02 and reference your name and phone number.