^I think the idea behind The Children of Kings
, as expressed in the author's afterword, was that since we now had more than one timeline onscreen, the books didn't necessarily have to be bound to an existing timeline. Or something like that. Although from a more pragmatic standpoint, I think the book was most likely written before the movie came out, and things were still up in the air about which timeline(s) Pocket would be writing books about going forward. I recall that before Marco Palmieri was laid off, and before I was pegged to write one of the abortive Abramsverse novels, Marco had asked me to develop a TOS novel which could be tailored to either continuity depending on what Pocket ended up doing vis-a-vis the movies going forward. (In retrospect, given what happened with the Abrams novels, that seems like a safer idea than what we ended up doing.) Mine would presumably have been adjusted to fit either one continuity or the other before publication, but maybe TCoK was based on a similar idea, telling a story that wasn't clearly bound to either continuity.
As for TCoK being before the launch of the Enterprise
in the movie, keep in mind that Countdown to Darkness
established the existence of an earlier Enterprise
that Robert April commanded until 2249. So maybe it could fit that continuity after all?