You can never start too early with catechism. And you can never speak too intelligently to kids.
My daughter is two. I’ve begun teaching her. We listen to sacred music (not so much for catechetical reasons but that I was being driven insane by her nursery rhymes), and sometimes I catch her singing “Laudate Dominum!” or “Magnificat anima meam Dominum!”
A few months back–overnight, strikingly–she started getting afraid of the dark when she had to go to bed. It was very painful, even though she is very brave. Sometimes I would explain to her that she had to go to bed and she would nod and put on a brave face while holding back tears, like a soldier who’s ordered on a suicide mission. Anyway, over time I developed a little speech that I would give to her when she got afraid of the dark. I would explain the three reasons why she shouldn’t be afraid of the dark: objective (there are no monsters; there objectively is nothing to be afraid of); subjective (our goal in life is to be spiritually free, and fear holds us back–fear is the mind-killer, fear is the little death); transcendant (as a child of God, there is literally nothing for her to fear). She no longer has fear of the dark, but she still asks for “the three reasons” almost every night, as a bedtime story. And one of her favorite parts is where I point to our icon of the Virgin and tell her that if she gets afraid she can pray to “Mary, your mother in Heaven” and she exclaims happily “Mawwy!”
And this is really the only theological justification I need for the Church’s Marian veneration. Our immaculate Mother is truly the porta cæli, the one through whom the graces abundantly flow, our tenderly loving mother, always ready to embrace us. We all love our mother first, before anyone else. The truth comes from the mouth of little children, and to those who are like little children the Gates of Heaven shall be opened. That my daughter is filled with Marian grace makes her an icon of the Church, one that I am truly thankful for.