"O God, Great Father" alludes to the gospel story of bringing little children to Jesus, especially in stanzas 1 and 3 (Mark 10:13-16). The Reformed view of God's covenant shows up in stanza 2, and the work of the Holy Spirit appears in stanza 4.
Stanza 5 is similar to the consecration prayer that follows the act of baptism in the Psalter Hymnal's baptism forms.
Bert Polman, Psalter Hymnal Handbook
The inclusion of children at baptism is taught in Heidelberg Catechism, Lord’s Day 27, Question and Answer 74 when it says, “Children as well as adults are included in God’s covenant and people” and Belgic Confession, Article 34 which says, “…our children ought to be baptized and sealed with the sign of the covenant…"