In Windows, copy whatever files you wish to be 'hidden' to an appropriately named folder...
Right-Click ONCE on that folder...
Select 'Properties' with a single Left-Click...
See 'Attributes' and check-mark 'Hidden'...
Left-Click on 'Apply'...
Left-Click on 'OK'...
And remember, natch, that unless your kids are about 3 years or younger, you could have asked them to show you how to do the above !!!
p.s. If YOU want to be able to find said folder later, you must
enable viewing of hidden files/folders...
Tools/Folder Options/View...