My thoughts would be to change kitchen and living into bedrooms, make laundry into a bathroom (ensuite perhaps), then extend out the back for kitchen, laundry, living room.

You’ll get some great plan advice here. Do you have the budget for an extension?
What parts of the house aren’t under the main roofline?

Do you need four full bedrooms to use as bedrooms or is one used as a study?

How much open space is on the block for an extension

what are the walls and floor made of, concrete or timber?

we need a site plan showing the width and length of your block, location and size of any other buildings (garage?) distance of the existing house to all four boundaries, where is north, describe your local climate and what are the walls floors and roof built out of and is the whole house original or is there an old extension ..some photos of the outside including overhead picture of the roof will be useful and the real estate plans have inconsistent dimensions.. please measure every room (ignoring wardrobes and cupboards) including halls, laundry, toilet, kitchen and bathroom and add the correct dimension to the plans

Thanks for great response from you all so far.
This shows the the property and it’s placement on the block which 14m x 36m

My budget for the extension would be up to 200k

By the plan , I'm guessing 60's or 70's build ? I'm also guessing wooden floors ? All of that would make matching everything more difficult than a modern build , but not impossible .

The back section doesn't look huge , assuming its roughly to scale , and the garage is a further problem .

I'm lazy , so I'd sell , put the $200k towards your new ( even if its old ) place that is bigger and has most or all of what you want .

Knock down/rebuild would be a lot more than your budget .

Amything else I would put in the not practical/too hard basket -- I suspect if your plan and layout is accurate , you'd either need a 2 storey extension ( expensive and hard to successfully do that era easily ) , or maybe dig under or jack up and add a basement . My head hurts at those though . . . . . . . . . . . .

Aaron, are there any houses in your areas with the garage in front? Worth having a chat with your council to see if it’s possible as it will free up your backyard.

Your block size is not dissimilar to mine. I’m forgoing a backyard garage for a front carport.

its difficult to be specific without all the extra info requested but something like this might work