Students Chace Harrison, Jalailah Jayne-Maree Jones, Zane Mellor, Addison Stewart, Jye Sheehan and Peter Dodt died after the incident at Hillcrest Primary School in December 2021.
The 11- and 12-year-olds were enjoying end-of-year celebrations on the school oval at Devonport in northwest Tasmania when a wind gust lifted the castle and several inflatable balls in the air.
Preparations for an inquest were put on pause for years until the conclusion of criminal proceedings involving castle operator and owner Rosemary Gamble.
Ms Gamble was in June 2025 found not guilty of criminal workplace health and safety breaches, allowing work on the inquest to resume.
A September 21 start for the inquest was confirmed at an administrative hearing of the coroner's court on Friday.
It will also sit on September 22, 23 and 25 before a break, with further hearings to be held in November and 2027.
Georgie Burt, Zane Mellor's mother, will be among six witnesses to give evidence in the September hearing block.
Tasmania Police assistant commissioner Adrian Bodnar, Ambulance Tasmania chief executive Nicole Ashworth and forensic investigators will also give evidence.
The inquest will be held at a conference centre in Devonport to accommodate more people.
Its scope includes an examination of the role of Tasmania's education department and the application of relevant national safety standards and weather monitoring.
It will probe Chinese company East Inflatables, which supplied the inflatable equipment to Ms Gamble's company Taz-Zorb, and what information and operating manuals it provided.
Inquest preparations had faced several hurdles, including a legal stoush between the coroner and Tasmania's workplace regulator over access to documents.
In the criminal proceedings, the court found Ms Gamble could have taken further steps in relation to the castle's anchorage, but even if she had, it would have made no difference to the outcome.
The "dust devil" wind event was impossible to predict, the court found.
East Inflatable's representative Andy Chen gave evidence at the criminal hearing, saying he couldn't recall exactly how many pegs were supplied with Mr Gamble's castle purchase.
Families of the children killed and injured in the incident have launched a separate class action against the state and Taz-Zorb.
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