What are some nonverbals to look for between parent/child interactions
and where can I look to get more parent/child information on
nonverbals?

I'm not sure if this is what you're interested in, but signing with
hands is becoming a popular way for parents to help their young
children to learn to speak.  At the most basic level, you make your
own simple sign for drink (for example) and every time you say 'drink'
you make the sign.  Babies can copy this sign before they learn to
speak.

There seems to be a lot of information and recommended books and
videos at: http://www.signingbaby.com/involved.html

Hope this helps,

Gremmy