The phrase "holy child Jesus" occurs only twice in the English Bible. Both are in the prayer of the Jerusalem church in Acts 4 (27 & 30). I'm intrigued by the significance of this phrase.
The AV is the only translation I can find that renders the phrase this way. Most newer translations render it "holy servant Jesus" or something of that nature. "Servant" is certainly a possible rendering, and could mean an emissary from a king, but I think that the usual first meaning, child, is better to indicate what seems to be the incarnational quality of the prayer.