No amount of polite notes changes by-laws or Environmental Protection laws. We had a neighbour who said the police had told him it was OK to have a party. Maybe they did but it made no difference – he was still pinged for excessive noise after hours.
In your shoes I would let this one go and hope it’s a one-off. If it turns out not to be, you can call the police if the next party breaches the standard local laws on noise (not after 10 pm on “school” nights or midnight at weekends). Otherwise, if it is excessive at any time of day or night, regardless of the above laws, you can ask your strata manager or committee to issue notices to comply.
If the proposed party does turn out to be excessively noisy, you can ask your strata manager or committee to send a letter saying there have been complaints and that any repetition will be dealt with by by-law breaches and/or complaints to police.