Jack, as far as I know the master file's preamble overrides the child's preamble, and therefore all the settings in the preamble are inherited from the parent. So, these for sure:
> \usepackage{apacite}
> \AtBeginDocument{\renewcommand{\ref}[1]{\mbox{\autoref{#1}}}}
and possibly these as well, if passed as options to the class
> the paper format
> the two-sided document setting
Cheers,
Stefano
