score:7
Your question is very broad, but I guess you are looking for inspiration at this point. I would recommend you focus on either the East Coast or the West Coast. There is a whole lot of nothing along the Great Australian Bight (south) and the "Top End" is likely to be a bit harsh and too repetitive for small children.
Here is a suggestion to narrow things down:-
This will give them something to look forward to and help them understand the trip.
Visit the Great Barrier Reef. Your children will be able to see fish and coral from a glass bottom boat. 3-4 years old is too young for snorkling unless they and you are very comfortable in the water.
Visit the Daintree Rainforest.
Fly Cairns to Brisbane (as it would be a 1,700 km drive according to google maps)
Travel down the East Coast from Brisbane to Sydney (about 1,000 kms) in a rental car.
There will be plenty to do and you'll have a range of accommodation options along the way. You can visit theme parks, national parks, look for migrating whales etc. Allowing 2 weeks for this would be a relaxed pace. Practically speaking, given you a travelling with small children, you will always be close to a supermarket or at least a petrol station if you need supplies or a stop.
If you wanted to see Outback Australia you would need to deviate from this path further inland. You could consider a visit to Western Plains Zoo Dubbo if you have time. There will be kangaroos. (The first ones you see will probably be dead on the side of the road).
The kids would enjoy the Powerhouse Museum and Luna Park. It's a large city so there are many possibilities.
Uluru as a well known attraction, but it's a long way from anywhere and I doubt your kids will be that impressed. Save that for your next trip.
If you can, avoid the school holidays in NSW and Queensland as this will lessen the number of tourists.
Upvote:3
So long as you keep your brains switched on i would not say there are any no-go areas, however due to the young age of your children I would stay close (ish) (3 hours) to major cities / towns. This is because i would hesitate to take toddlers to very remote areas where they cannot understand the risks involved, and if something goes wrong (snakes/spiders/crocodiles in remote areas) you are a long drive & flight to the nearest hospital.
Having said that - I would reccomend a couple of places near Melbourne :
Which should be good for little ones :)
Upvote:5
Here's a brief list, because your question is very broad:
Upvote:5
A couple of additions to @dlanod's excellent answer, from my own experiences exploring a good chunk of Australia:
Canberra - the Science museum is a must, as is the view from the Black Mountain Tower. Tidbinbilla tracking station is rather good if your kids like Astronomy.
Western Australia - the land around Perth and Fremantle is beautiful, lots of places to see kangaroos and other wildlife. There are some of the most amazing caves I have ever seen.
An hour from Sydney you have the Blue Mountains - again, a wide range of outdoor attractions.