So they don't get bigger than 70cm up there?
Good on you for releasing the bream. One or two flatties is enough for a feed and I don't like freezing fish, the upside is that you have an excuse to go catch some more! I, as with you, don't like keeping bream at all. They always go back.
Also, I'm not sure in Qld but in NSW it is illegal to have undersize fish in your possession, that means that any undersize fish must be returned immediately. If you're caught with undersized fish, dead or alive, fisheries will ping you. As you said two of those flathead are undersize.
Just a friendly tip, you may want to invest in a battery powered air pump for your make shift live well, it will ensure that the fish have a higher survival rate. Tape it to the bucket and a decent one will only set you back around $40. (cheaper ones have a nasty habit of not being able to pump the air at a consistent rate)