When I started this blog in 2011, it was hard to find out about fireworks in Perth. The government department responsible used to publish a PDF on their website, but it was basically invisible on Google.
But at some point that changed, and they made the information much more accessible. I kept posting here, adding links and fixing occasional mistakes, but I think the time has come to stop.
My final answer: go check the Schedule of Fireworks Events on the website of the Department of Mines, Industry Regulation and Safety. (It was probably ranked above this one on your google search.)