The funeral rites for children are not intended to be celebrated by rote: always the same for particular ages. The minister is urged to awareness of the situation, as well as dialogue with the family. I can imagine a pastor or staff member laying out possible options, and exploring a yes or no decision on particular rites. One example is given in OCF 235:
The minister, in consultation with those concerned, chooses those rites that best correspond to the particular needs and customs of the mourners. In some instances, for example, the death of an infant, only the rite of committal and perhaps one of the forms of prayer with the family may be desirable.
This would not be a decision for the pastor alone. But a sensitive pastor can lay out the options as well as briefly explain the purpose of the vigil, the funeral Mass, and the rite of committal. The family may seem indecisive, but can be nudged to a solution that suits the best. It is well to keep in mind the purpose of these rites:
236. In the celebration of the funeral of a child the Church offers worship to God, the author or life, commends the child to God’s love, and prays for the consolation of the family and close friends.