I wouldn't allow a mouthy pup around little kids until you get it under control. When my male got past that stage, he was taught to "down" when approached by children. He ended up doing this without being told later on, so my full grown male was never a threat to children (from their point of view). He loved everyone, though... as long as they weren't a clear threat.
Wrath of Grim z Dragon
"Mr. Grim"- Threaten my handler. I dare you.