Hello Dr. Bamford,
My name isXXXXX'm a licensed attorney. Glad to try and help out.
I'm pleased to share the following information with you.
Good news. Yes, I agree you folks have little (actually nothing) over which to be alarmed or concerned. In other words, I believe you can indeed reassure the local Council, as follows. Copyright, in terms of the scope thereof, is defined by the Australian Copyright Act 1968, as amended. (There are certainly other enactment, such as the Copyright Amendment Act 2006, but speaking broadly there's no need to go into great depth.) Here's the botXXXXX XXXXXne. Your understanding is indeed correct, in that for published works such as you've described, these items are long (decades) out of copyright. You're also right to mention the concept of "fair dealing" (spoken of as of "fair use" in other jurisdictions). However, that's a secondary argument or fall back position, so to speak, and you need not even get there. Meaning, with these items being so clearly and so long out of copyright, while fair dealing is certainly a logical and relevant defense against a potential claim of infringement, it doesn't even need to be raised given the application of a proper counting of the 70 year period. So, what it boils down to it that you're quite safe, indeed, and I fail to see any cause for alarm or concern.
If you have a follow-up question or need clarification, please just say the word by using "reply" to reach me.
I truly hope all works out for you and that the event is a smashing success!