These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Author's Saving Throw: Comments made in-story by the Future Children, as well as one Author's Note, suggested that several of the canonical Children had been Adapted Out (specifically Yarne, Nah and Kjelle), particularly since Mal didn't mention them among the ones he was still to find (the others were part of his crew by then). When this came to the Author's attention, he admitted the mistake in a later Author's Note (as well as showing confusion at forgeting about them since he's got plans for them), and he salvaged the situation by having Mal mention that they "still had to find them" (suggesting that they hadn't been found earlier, and rather than being forgotten or non-existent they were probably not at their in-game locations yet).