SSRS 2012, push permission changes down the structure?
@Matthew, 
Given that you do not want to revert to parent security on your sub-folders and children reports, I think your only option will be to write some custom code which accesses the SSRS Web Services API.  I've done something similar using powershell for one project and a C# script task from SSIS for a different project and should work well although it won't be accessible from the SSRS management portal.  

I'm 99% certain that there is no functionality within SSRS that will directly handle your request out of the box.