The single hitpoint seems odd to me, though. Certainly the primary scare and creepiness factor is in trying to find what the Child is, and once that's past the ease of killing it keeps a bit of guilt-factor for heroes who might still wonder if they've done the right thing, to kill a child- but still, it just stands out as odd to have a single hitpoint.
Beyond that, beautifully creepy.
There's a point. 16d4-32 averages 8hp (mean result on a d4 is 2.5) and caps out at 32hp (although less than 1 in 4 billion Children will have this much!). But the 1hp thing is very flavourful, if you wanted to keep it...
Edit: Yeah, what Iames said, only 3 minutes sooner.