I have a 10 month old black lab who is very loving with us most of the time.  Twice now she has been aggressive with my children by growling, snapping and lunging for the eyes.  She also did this to my nephew.  She likes some of their friends while we have to hold her back from others.  I have been present when all these instances occurred and no one was being mean to her.  She has never been mistreated and is currently in puppy training.  I don't know what to do about this and hate to get rid of her but don't want someone to get hurt.

you say she goes for their eyes, are they staring at her dogs react badly to staring, in the dogs world its threatening and children tend to be at eye level what advice does your trainer give you?

I think maybe he is at an age were he is showing a bit of assertiveness? and if the child ran off or was frightened he got the desired effect.
Does he go to obedience classes, maybe someone with more experience could help like a behaviourist? as it wouldn't be right to advise with children being involved.
:)

Could she be coming into season?
You say that "she likes some of their freinds while you have to hold her back from others."  Sounds as if she is not completely at ease with all children in which case it wouldn't take much to trigger a reaction.  Something that you wouldn't even notice maybe.

Your best course of action would be to have the vet check that everything is okay physically and find a trainer/behaviourist that will help her without using negatives or punishment.
Sally