PM visits Davenport to pay his respects

"I want to extend our deepest sympathies to the five families in particular who have lost those precious young ones and we think also of the families of the three who are still in a terribly critical condition," Mr Morrison said in Hobart ahead of the trip.

"We think of the entire community that is just heaving with sorrow.

"As I said yesterday, there are no words, only prayers, for our fellow Australians in Tasmania, and for the community that will carry this burden. And it will be a heavy burden. It will weigh them down."

More than a million dollars has been raised in the community to support those mourning the tragedy.

The children died after a gust of wind sent a jumping castle 10 metres into the air during year-end celebrations at the school on Thursday.

Eleven-year-old Addison Stewart, and Zane Mellor, Jye Sheehan, Jalailah Jayne-Maree Jones, Peter Dodt, all 12, lost their lives, while three others are fighting for life.

Mr Morrison says an extra $800,000 will also be made available to fund trauma counselling.

Some $250,000 will go to first responders involved in the aftermath of the accident and $550,000 to the broader community.

The money will be paid to Tasmania's Primary Health Network over 18 months and will add to $500,000 the Tasmanian government announced on Friday for counselling.

"We know support won't just be needed in the next few weeks, it will be needed for many, many, many months, to try and begin that process of healing," Mr Morrison said.

Grace Johnston, who is raising money for Zane Mellor's mother, described Zane on Friday as a beautiful, caring, and gentle soul who kept achieving despite his challenges with autism and ADHD.

She said she wanted help his mother Georgie Gardam as she won't be able to work following the tragedy.

"Georgie is the most amazing mum, she never gave up and was by his side every step of the way encouraging, loving and fighting for him," Ms Johnston said on the GoFundMe page.

"This has shook so many people and the community and we want to do anything to help make things a little easier for her at this hard time."

Peter Dodt's aunt Tamara Scott also set up a fundraising page, describing her nephew as a young boy who was full of life and adventures, while Addison Stewart's aunt Meg Aherne said she was trying to help her niece's family pay for a funeral and other bills.

"They have another daughter and son to take care of and I'm hoping to alleviate some of the stress of bills," she said.

"Everyone is devastated, she was always such a sweet kind, old soul - We all love you Paddi Melon."

One of the fundraising pages, posted by Devonport local Zoe Smith, had raised just under $1 million by late Friday, with the money to go to Hillcrest Primary and its Parents and Friends committee to be distributed to affected families.

Meanwhile authorities continue to examine whether the inflatable castle was properly tethered.