When children have been baptised as young people, it is with the understanding that the parents and godparents will nurture them in the faith and practice of the Church. When the young people are old enough to make an initial commitment of faith by seeking to receive Holy Communion, they are encouraged to do so. This is usually from about the age of seven, however this depends on the Christian maturity of the child. It is not uncommon for people much older to receive their First Communion as well.
The important thing about First Communion is that the person being admitted, should make the decision themselves. It is not appropriate for mum and dad or someone else to emotionally pressure them into being prepared and admitted.
The Easter season is a preferred time of the church year for this to occur.