It's been an interesting thread and whether it is over or just starting, it is an important question. I take it your ultimate question is probably "Why" should we look to nature at all, regardless of whether we look at children or any other phase of life?
Why does "is" give rise to "ought"? And you definitely have another step in that process in getting from is to ought.
Of the alternatives in Torquatus it seems to me that "anticipations" makes some sense to look to as a foundation of pleasure, but why does pleasure exist at all for us to follow?
I think we're on very important territory here and the resolution comes very close to (paraphrasing Nietsche) whether we choose to say "yes" to nature or "no". Nature allows us to do either and it is ultimately up to us to decide and pay the price / reap the consequences for our decisions.
Regardless of what we as individuals decide, Epicurus seems clearly to have chosen to say "yes" to a view of nature based on sensation/ feeling, rather than abstract logic, as the standard of a proper human life.