Two other sections in the Rites of Pastoral Care of the Sick are referenced for a child who is suddenly near death:
173. If sudden illness or an accident has placed an unitiated child in proximate danger of death, the minister uses “Christian Initiation for the Dying” (PCS 275ff), adapting it for use with a child.
174. For an initiated child or a child lacking only the sacrament of confirmation, who is in proximate danger of death, the “Continuing Rite of Penance, Anointing, and Viaticum (PCS 236ff), may be used and adapted to the understanding of the child. If death is imminent it should be remembered that viaticum rather than anointing is the sacrament for the dying.
When is the discernment for imminent death? That determines if the child (or adult) will be anointed or if the focus will be on the last reception of the Eucharist.
Also note the broad leeway given for adaptation in these rites. How would a priest or minister start adapting? I would think the “emergency” rites should be attended to first, and Scriptures and prayers used that are within the comprehension of a child. I would think that “within conprehension” doesn’t mean a 100% dumbed-down version, but a liturgy in which the language stays largely or partly as is, but there’s a pastoral sensitivity to the comprehension of the child. What would change? I would think the various greetings, welcomes, and explanations, plus taking time to pause for catechesis a few times, like at the important moments.
With this post, I’m going to take a pause from this examination of the Rites of Pastoral Care of the Sick. Next up will be Viaticum, Eucharist for the dying Christian. We’ll be observing the holidays both in and out of town, and while posting will not disappear altogether, I’m going to hold off on resuming PCS until the new year. Including the appendices, PCS counts up to 305 sections. I’m anticipating another month’s worth of posts, and then we’ll pick up RCIA in plenty of time for Lent.
Catholic Sensibility 
The few times I’ve used these, the child was unconscious or too young to understand anything of the Rite. I always confirm when there is a danger of death, even if the death is likely not “imminent” in the sense of a few minutes or hours. If the child has a prognosis of death within a week or so, I’ll definitely confirm.
In this case, the sacraments are for the dying child, the ritual is for the parents and family, so I tend to use the fullest measure of the Rite.