OK, speaking as an ex SA firefighter now living and working in Central West NSW I offer the following which may or may not be applicable to SA.
Firstly, most grain storage facilities over here are surrounded by a reasonable amount of mineral earth plus it takes a fair amount of radiant heat to severely damage grain. So not a huge amount of effort needs to be applied to the grain.
Next take a look at the house occupants, are there any that are old or infirm (consider evacuation) where are the young fit people( they should be on your trucks!!!), they should be able to help protect their homes so you can concentrate on the others.
Finally, as Alex said, protect the pub!!! I know it was meant as a joke but take some time to think about this. Just imagine the affect on a small community if they lose their pub whether it be through fire, bad management or whatever, the community loses much more than a watering hole. There goes their social networking place, meeting place for local groups, sometimes local shop as well as employment for some. There are two small villages in my group where the pub is the only retail business, in one of them the publican is the brigade Captain, the other the publican is a Senior Deputy (equivalent Lt.1) so the best way to turn out the brigade is to ring the pub!!!
Once again, no real right or wrong with this scenario, just the way I think and thanks bajdas for the opportunity to express it.