Would you use "tu" or "vous" when talking to the following indivisual?

Would you use "tu" or "vous" when talking to the following indivisual?

"tu" to people that we know very well, or to speak with children.
"vous" to those with whom we are not intimate, like a teacher, the cashier, the hairdresser, dentist

"tu" pour des personnes que l'on connait très bien, ou pour parler à des enfants.
"vous" pour des personnes avec qui nous ne sommes pas intime, comme par exemple un professeur, la caissière, la coiffeuse, le dentiste

We use "tu" for our age group and "vous" for the elderly since its formal