Now I have a son I have found myself not very self conscious in his company. I play with him whilst doing a robot voice when playing with robots and doing slightly differing voices with different animals and I don't notice the people who are in the room. I would never have thought it possible that I would so much as hum in front of others, but I can't help it. You notice that everyone else who has kids does the same so you feel like you are in a gang, albeit a gang of tired, skint and cranky adults. 
Went out for a drink and saw this occurring as I spoke to Jacob about using crayons on a napkin. My voice had a playful tone and maybe sounded excited at the prospect of my napkin having some colourful scribbles on it. 
Back when my sister was young I spoke to her like she was twenty, I thought talking to them any other way would hold back their speech as noone speaks in gobbledegook unless ofcourse they are welsh.