Overlooked in the funeral Lectionary is this selection suggested for the funeral of a child. You can find more Catholic suggestions in the Order of Christian funerals right after the adult readings, in chapter 14.
The framers of the rite suggest verses 3 through 5 of Ephesians 1, but I think the longer section, used as a canticle for Evening Prayer on Mondays brings good material to bear.
The brief form of the reading begins:
Blessed be the God and Father of our Lord Jesus Christ,
who has blessed us in Christ
with every spiritual blessing in the heavens,
as he chose us in Christ,
before the foundation of the world,
to be holy and without blemish before him.
In love he destined us for adoption to himself
through Jesus Christ, in accord with the favor of his will,
This may be just right in length for a funeral. It sums up the writer’s point: that God’s care is so great, so loving, and so full of foresight that before the Earth was formed out of the leftover dust of the solar system, God had his eye on us, and claimed us as his own.
Of course, any of those few times I see “adoption” in the Bible, my senses perk up.
And the rest continues:
for the praise of the glory of the grace
that he granted us in the Beloved.In Christ we have redemption by his blood,
the forgiveness of transgressions,
in accord with the riches of his grace that he lavished upon us.
In all wisdom and insight, God has made known to us
the mystery of his will in accord with his favor
that he set forth in Christ as a plan for the fullness of times,
to sum up all things in Christ, in heaven and on earth.]
Any funeral of a young person is exceedingly difficult. In any sane world, parents should not be burying their children. But we know it happens. We might not understand the difficult question inevitably asked: why? But the answer to who is just this: Christ. Christ redeemed us. Christ forgives us. And God’s plan is for the fullness of times, in the summation of all things every living, that we all will know God’s favor in eternity. And at that time, the sorrows of our mortals lives will be a fleeting thing. And then we will have the reunion that now seems like a bitter and sad promise.
Catholic Sensibility 
Well, consider that, in the preconciliar ritual, there were no requiem masses for children who died before attaining the age of reason (7 yrs became the standard marker, but I think it did once vary more in the more distant past) – “infants” in the Roman legal terminology. Baptised infants were given a different ritual that in a sense was a celebration of their sainthood – the Missa de Angelis was the commonly used Mass setting for that ritual, and since the death of young children was so common, that setting became very widely known. One can imagine this ritual practice was capable of prompting very different reactions from grieving parents.