This was a real question that I recently received!!!
I will first answer this question with a question…Has anyone heard a more heartwarming question than that? How happy would St. Pope John Paul II be to hear that question? What a great example of 'the new evangelization.' Let me first give some stories of young people evangelizing and then some practical examples.
Most traditions put the age of St. Tarcisius around 12 years old. At St. Tarcisius' young age he has given the Church an amazing testimony and example of faith in the true Presence of Christ in the Eucharist. He died while protecting the Blessed Sacrament while on route to taking it to prisoners.
For the last hundred years, Catholics around the world have been inspired by the story of St. Maria Goretti who died at the age of 11 to keep her purity. Her example even inspired the man that killed her to convert and accept Christ's forgiveness. That is some evangelization!