very concerned

Question
I adopted a 5 month old mix from the shelter.
It has so far been highly timid and shy.
I am scared it might bite the children that come here to play for it bares its teeth often.
I do not know how to correct it and hate to return it, It is so sweet otherwise, but hides when people come to visit and highly shy.
I have two children it does not like especially either.
Please help me.

Answer
This sounds like the classic fear biter.  The dog likely was not exposed to children before it was 12 weeks old, or was abused by children when young.  Such dogs see the best defense is a strong offense.  The easy, logical thing to do is to return it.  Chances are, the shelter kills much nicer dogs every day for lack of homes.  

No, I do not have a stone for a heart.  The dog is still young, although well past the age where it accepts new things easily.  You can work with it.  Control your fear and stress when it is around children.  It is hard to fool a dog.  Greet the children in a happy tone of voice.  Hug them.  Do not let them approach it, and never let them corner it.  Instead, leave it, and go to the the children and quietly interact with them keeping things low key but happy.  I know, they are kids.  Do the best you can.  Dogs have a powerful urge to be part of the group.  If it approaches them, have them hold out their hand below its face and let her sniff it and lick it. Do not let them pat the top of its head.  dogs like a butt rum much better.  Perhaps arm them with treats.  They don't have to be fancy, even a little of her kibble will do.  Be very quick to praise it for any sign of accepting them.  Pet it, sound like you mean it when you say good dog.  Like children, there is no substitute for starting out right.  Still with patience and love, you may be able to save it.  Above all, do not let the children push it to where it does bite.  It is so easy to teach children to fear dogs.