Thr question asks about babies and the answer ia ghu, rather thqn ghupu'
The plural suffixes are usually optional in Klingon. wej QongchoHpu' ghu means both The baby hasn't fallen asleep yet and The babies haven't fallen asleep yet.
Thanks for the clarification on singular multiples. I put more emphasis on clarifying if one or multiple babies sleeping.
Answers with and without the plural suffix are accepted, and have the same status as preferred answers, so your clarification is not wrong.