score:5
Your embassy has already told you that your children have to be added to your visa, and the Australian Immigration website says the same:
Children born outside Australia to permanent resident parents will need to apply for and be granted a permanent visa to be able to enter and remain in Australia with their parents.
Now that wording is a little ambiguous: they'll (obviously!) need the permanent residence to enter and remain, but you're asking about entering only.
In practice, if you showed up at the border with valid eVisitor visas for your younger children, they could turn you away because they'd have very valid grounds to suspect they're not leaving, but they would probably let you all in. However, this would almost certainly cause you hassle:
So I'd recommend filing the paperwork to get your children added to your PR right now -- it should only be a formality, although Abbott knows DIBP can still take their sweet time processing it -- and cooling your heels until it's granted.