Put all files i a book file, take care that page numbering does not change, check update files in the book panel, update all numbers in the book panel, then you will not need the book panel anymore.
Maybe someone offers a script, which makes it simpler. You could ask in the scripting forum.
@Quin – you could use Peter Kahrel's script "Batch process":
The script (batch) processes files. It can be used to export InDesign documents to PDF or other formats, to convert QuarkXPress and PageMaker documents to InDesign, to update large numbers of InDesign documents to a newer version, e.g. from CS6 to CC, and to downsave documents to previous versions of InDesign.
I did not test "Batch process" with CC-2015 yet…
Trying to avoid the tedium
Batching can be done via scripting, but you could also auto convert when you save via a script. So this AppleScript (OSX only) checks to see if the front document has been converted and if it has saves back to the same path, otherwise it runs a normal save. So you could save the script to your scripts folder and assign it the Command-S key command and you would not get a Save As dialog when you try to save a converted file. Should work for any version of InDesign.
tell application "Adobe InDesign CC 2015"
tell active document
--get the file's path and name
set filepath to file path & name as string
--if it has been converted save to the same path with no dialog, otherwise save
if converted is true then
save to filepath