Congrats on success, the last one looks like a Brachychiton rupestris seedling, great forgiving abusable trees just keep them DRY!@ first repot cut the tap root off completely & plant with a tile or something similar underneath to spread the roots sideways.
For the first I would go with a self sown Callistemon that has blown in from nearby. However you say there are no trees nearby, if it is a mallee etc there should be some scent when you crush a leaf.
Matt
42 Mice ~Imperfection
"Experience is a hard teacher because she gives the test first, the lesson afterwards." ~ Vernon Sanders Law
"All the knowledge I possess everyone else can acquire, but my heart is all my own." ~ Johann Wolfgang Von Goeth
"Bonsai becomes great when growers start trees they know they will never see in a pot"