I like this, and think the objections to the rationality of the narrator are a bit overblown. They seem to proceed from the assumption that all suicides are the same somehow, that there aren't as many moods of death as there are of life. I, for one, found the detached mood here quite believable, and in keeping with the tight form. And the word abyss is the perfect foil for all that order that has come before: it conjures a calm chaos.
Whether the children's moon is sufficient to turn the poem on or to turn aside the act of suicide for any specific reader is not the point. It is enough for this narrator. I always try to take a narrator at his or her word, and any further work done on the poem should address itself to convincing us of that narrative integrity. That moon works for me as a sort of childishly irrational moment to stay the hand of the more rational adult, and so I did not question its plausibility.
I do like Andrew's suggestion of the using the past tense in the opening of the poem: it adds a bit of drama to reason.