I was 7 years old when I committed my life to Christ and was baptized. What I understood is that rejecting Christ and dying in my sins resulted in my going to hell for eternity. The alternative was yielding to Christ, letting Him be the ruler of my life and joining Him bodily in heaven when I died. I chose to avoid hell and go to heaven.
I think as adults we make the choice more complicated than it is. My childlike faith believed that Jesus is God's son, that He died on the cross for my sin, that He rose from the dead, and that He is seated with His Father in Heaven and that He will return one day to take me home.
Why are we surprised when children make such a clear and obvious decision?
Sure, there have been times when I've disobeyed. But, I've never wandered far and have always repented out of a true desire to be pleasing to my heavenly Father. The sense in which I mature, I believe, is in comprehending the depth of His love for me and the incredible blessings that are mine in this life from following after His Word.
My two youngest sons (aged 8 and 10) will be baptized this year. My other three children (aged 21, 18 and 15) are strong Christ-followers and I'm not worried about their continued walk. God is faithful!
Finally, I'd have to say I probably witnessed more as a young child than I have as an adult. I'm working on changing that now.