First Overnight Walk with 3 & 5 year old? Suggestions Please

Hi,
We have been gearing up and doing some day walks with out two kids! They can easily handle 6km of reasonably challenging terrain (considering their age!).
We want to head out on our first over-nighter and have no idea where to start. We have done a lot of bush camping so the kids are used to being out with out facilities and we want to go that step further now
We are looking for somewhere where you can overnight camp that is not accessible by car - walk in only - we are outer east so if out this way it would be great, but don't let that limit your suggestions. I guess we are looking for a walk with enough interest for the kids and a little bit of a challenge as well! (but not enough to scare them off over-nighting!)
My husband and I are pretty excited on starting out next adventures! Hit me with your ideas!!
Thanks in advance everyone!
We have been gearing up and doing some day walks with out two kids! They can easily handle 6km of reasonably challenging terrain (considering their age!).
We want to head out on our first over-nighter and have no idea where to start. We have done a lot of bush camping so the kids are used to being out with out facilities and we want to go that step further now

We are looking for somewhere where you can overnight camp that is not accessible by car - walk in only - we are outer east so if out this way it would be great, but don't let that limit your suggestions. I guess we are looking for a walk with enough interest for the kids and a little bit of a challenge as well! (but not enough to scare them off over-nighting!)
My husband and I are pretty excited on starting out next adventures! Hit me with your ideas!!
Thanks in advance everyone!