Then a 3000km drive back home again. This sounds horrific! Probably in a car with hot vinyl and a busted AM radio, too. And to not even stop at the Big Banana! I hope you go there one day, as it's interesting for history and botany as well as for kitsch, and worth a visit.
Speaking of food and this is not my family thing, more of a general observation about 1970s Australia kids were never allowed to make their own sandwiches, or "sangwidges", as the olds would say. If you dared to slip a hand inside the Tip Top bread bag, someone would snatch it away from you. Two flabby white slices would then be engulfed in margarine, with just a dab of Vegemite or whatever in the middle. "There yar. That'll keep ya going 'til tea."
I once got busted for wiping the marge off on a tree, and also for eating just the crusts (which had escaped the marge) and frisbeeing the rest over a fence. I hated margarine so much and couldn't understand why it was compulsory. I've eaten plain, dry bread many times and not once has it killed me! Or glommed up my gullet!