The NewPerson notecard in the ChatBack system is what your child says the first time they meet someone. So keep in mind something a child would say to a stranger, such as:
I don't know you
Hi %, do you want to play? My name is Debbie
You can safely use the % in the NewPerson notecard because your child will only address the same person once with this card.
Next, configure the Speak2Me notecard, which is to be used for things your child says after they have met the person.