child's room vs sleeping room

child's room and sleeping room both are nouns.

Word	Noun	Adjective	Verb	Adverb
child's room	Yes	No	No	No
sleeping room	Yes	No	No	No

As nouns, sleeping room is a hypernym of child's room; that is, sleeping room is a word with a broader meaning than child's room:

Other hypernyms of child's room include bedchamber, bedroom, chamber, sleeping accommodation.

child's room (noun)	sleeping room (noun)
a bedroom for a child	a room used primarily for sleeping