Get a hold of your service plans, where is the sewer line? It may be mor economical to turn the fourth bedroom into a bathroom and the study into 4th bedroom by adjusting the wall to give greater space into the new bedroom. It all depends on your budget, anything is possible, eg Approx $100k conservatively the reconfigure kitchen and extend laundry out. If you want to create an ensuite it will be another plus. You have to weight up pros and cons of moving against renovating. Just shifting has hidden cost that is typically $100k. It is all the hidden costs. Then if you are wanting more bedrooms another $100k per bedroom and it all mounts up. It is often more economical to stay and have a 10 year renovation plan. Your family is going to change so much, even in five years eg a play room will not be necessarily warranted but a study area will be. You could square off the front and make a master suite, later move the kitchen to the current lounge and a ‘great’ room down the centre of the house. This give more more open and multi usable space. And could be done over stages.

First up draw up a plan to scale with dimensions. Real estate plans are approx only. You may be able to take out kitchen wall rotating it to extend the hallway. Open up the living dining wall as much as you can. If you can get plumbing to other end of house to serve the spare bedroom or near front door would be good. Get a plumber in to quote on options

Most of the external walls appear to be brick , so adding on is going to be more expensive , especially as you will have to ry and match the wooden floors to look good -- you might get away with tiles in the laundry, but to add a toilet or bathroom there is then only accessible off the kitchen or possibly Bed 4 ( even that may need doorways cut through brick ? ) .

The 3 thoughts I've had would be to turn the fridge and that whole cabinet by 90 degrees -- that will hide entry into the bathroom a bit more , and open up the kitchen visually .

Thought 2 is that the dining doesn't look overly utilised -- can that be a Work From Home area or similar too ?

And thought 3 is the most off the wall -- have you considered using the larger shed as a bedroom , an office , etc ? It does look like un-lined tin , but it is there , so depending on what the floor is , etc , have you considered that ?

And on that note , or maybe thought 4 , if that isn't practical , have you considered a relocatable and/or granny flat etc . Relocatable has the advantage that you can buy or hire , maybe cancel or sell in a couple of years , or 10 years ?

Anything is possible , but if you work on that $100k guideline , is it worth it now ? When you sell ? To keep the peace /

Just in case the above $ isn’t scary enough you’ll also need to add $ for the plans/permits/paperwork. $25-50k. Unfortunately small Renos incur pretty much the same paperwork costs as larger renos. The best bang for your buck is a master plan and staged works. Most permits will last two years for commencement so a Master Plan is a good approach.

My ideas, work on $3000 per square metre for renovation, could be less. Your plan doesn’t show, but I’m assuming there is a step down from existing entry into lounge, and then another step down to existing study. Looks like study and bed 4 are already an extension as they have a flat roof. I would convert laundry and part kitchen into new toilet, bathroom, laundry room. I would move existing entry to the lounge room on lower level. I would create a new bedroom where existing meals area is. I would create a new master suite using bed 4 and study. I would extend house into existing deck area. Keeping plumbing where it is for sink and place an island there with L shaped plan for cupboards and appliances. Create a new dining room with bifold doors onto existing deck. This is a complete dream of what your home could become. You have a good block with a solid neat home. You could plan the modifications over time. Have the end result in mind, then arrange practical stages to achieve the end result. You can utilise one bedroom as the guest room combined with office.

Oh my goodness! You’re all so helpful. We appreciate you taking the time to reply with your ideas and advice. It seems turning the bed 4 and study (existing extension) into a master and ensuite might be something to explore. And something with the kitchen is needed to! Definitely lots to think about.
Yes, the current entry is a step down to lounge and step down again to study. The sloped block makes things tricky again.
Thanks so much. Love to hear more ideas and advice too!