Cancelled flight and 7 hour wait for 8 month pregnant mother of 2 toddlers

We went to Sydney airport this morning at 9.30am for a 10.55am flight to Adelaide. The boards and announcements said nothing about any cancellation issues. We printed our boarding passes at the kiosk for our flight and joined a queue for 20 minutes for bag drop, to get to the counter and be told there was no flight to Adelaide. There was no current plan to deal with the cancellation of the flight, we needed to step aside and wait until there was a plan! After 1/2 hr we were told to make a queue at counter 26 to be given a new flight. No one came to work at the counter, as there were no more flights by Jetstar to Adelaide - all of their services were cancelled! Despite my obvious distress, being 8 months pregnant travelling with two small toddlers, Jetstar staff did nothing to help us. After another 1/2 hr of waiting in the 'queue' staff started walking around trying to find people on their list that they had found flights for. We weren't on it. Finally at about 12pm we appeared on a second list and were given a flight on Virgin at 4pm and a $10 food voucher for our trouble. The Virgin flight was then delayed 45mins and we got home at 6.45pm. A couple of nice fellow travellers gave me a chair to sit on and offered me a cup of tea or water during the chaos, but Jetstar staff were the most ignorant and inconsiderate people I have ever had the misfortune to deal with at airports. Never again.