I have seen the 2 types of aggression that have been experienced here;
the protecting aggression, and the unstable, uncontrollable aggression.
I have also seen the shades of grey in between,but usually the ones that
are trying to protect their property and people will have strict definitions
of family and non-family and will never bite or attack one labeled as "family".
The dogs of the other category,as Dennis describes, however you never know who
they will single out or when or even why they react- some of these are not even shelter
dogs with a past,they are just badly wired.
It sounds as if your dog is just protecting her people,but as Bina said the kids are
the priority,its a shame too since she may just be overly protective,but I don't think
anyone could tell you for sure.