Q. Do I still need to include a blank parent_child.csv file in the import zip if we are not setting up parent/student relationships?
A. The parent_child.csv file is optional and thus is not required to be included in your import zip file.
Depending on which version of the importer you are using, there are either three required files (users.csv, classes.csv, and roster.csv for version 1), or four required files (manifest.json, plus the previous three for version 2). There are only three files that are required in each full import and they are: users.csv, classes.csv, and roster.csv. The rest of the files are optional and should be included within the import zip as necessary.