I've backed up momentarily from the Toon head to first understand the proportions of a childs head versus an adult head.
This link helps explain it...https://www.mybluprint.com/article/c...ng-proportions

Before jumping into zbrush I'm using Photoshop(liquify tool) to test the theory first.
I'm using the Daz Genesis 8 male default figure and a baby head photo I found online for reference.

A drawing from above link overlayed on the G8M and baby heads.

Reposition nose, mouth and chin vertically...

...then horizontally as the article suggests for child proportions.

Angle the nose and chin as mentioned.

It does look youthful without further adjusting like the ears,head and frontal view proportions.

On to the next step then.
Baby steps folks.