Look at the person in profile. The more prominent
the features, ( long or prominent nose, receding chin, sloping fore head
) go with a long lens: 135mm. With a flatter profile ( all the
features close to a vertical plane ) you need a shorter lens. 80mm or
even 70mm for a child. The point is: the more prominent the
features, the further away you want to be.
And bag the AF. Put a small 40Watt lite next to you to get a catch lite
and focus exactly on that.
Hope this helps Bob Hickey