If you know the child is feminine, wouldn't you just say "knabino". I see that "Infaneto" is baby. http://esperanto-panorama.net/vortaro/eoen.htm http://www.gutenberg.org/files/16967/16967-h/16967-h.htm
I found "estaĵo" for "creature". I wonder what language that one is from.
knabojn is the accusative (the verb is being done to them). Knaboj is the dative (doing the verb).
e.g. Knaboj manğis panon. Knaboj is the dative and panon is the accusative.
Vi amas min. Vi is the dative and Min is the accusative.
Mi estas vin. Mi is the dative and Vin is the accusative.
To make a word go from dative to accusative, add an -n to the end of the word.