Nice place! Get moving on those grasses though, Aussie fear of fire lol. Do a ph test near the hedge, assuming it's a pine or cypress of some kind, and the soil will be on the acidic side, and normally also hydrophobic. Therefor I'd suggest a path beside them, if it'd make sense (ie, lead somewhere useful), followed by a mix of citrus and blueberries if its not going to cast much shade (the hedge being northerly aspect for you guys), or just blueberry and other acid loving plants if not. I'd then go with a rhubarb, comfrey, horseradish type of mini-hedge followed by the main vegetable gardens. These are awesome at providing great nutrient cycling, mulch, beneficial insects, and soil improving. The bonus of your hedge, and the reason behind locating this for a path, is the clipping material would be a great source of mulch for the acid loving blueberries.
Another thing you should consider is isolating at least a part of this natural grassland for observation. Clearing out all the local wild plants, often before properly identifying what is there, can be a mistake. Get some largish rocks, make a pond, and edge it with this grassland and then watch it for a year or two would be my advice. I mean, when I look at a photo like this, and imagine all the insects that call it home, the amazing little flowers, and deep rooted plants, I see a mini lab in action. So much more inspiring and beautiful than heavily manicured and fertilized lawns.
As to excess water on this side, I would doubt that. A hedge such as that would suck up most of it, and the soil underneath would be a deterrent to any trees tying to get to that occasional creek. In fact, if the hedge and creek are entirely your own, you may want to hugelkultur a good portion of it, especially if the only thing it is blocking (not prevalent high salt laden wind for instance) is the access to the creek.
Oh, and my final piece of advice is, start small. One raised garden bed say 4 mtrs by 1.5mtrs (located close to the house), and a pond, while you get the "feel" of your site is often the best way to go. The first year its good to think about what needs more shade, what areas are best turned over to wildlife, what animals you'd like to keep etc, and develop your overall design. In the meantime at least you'll be getting a start by growing some food.
Cheers and have fun