Those terms and conditions are more problematic when someone earns money from their images i.e. a photographer as the Terms try and take the copyright of the image and transfer it/share it with FB. But if you continue to read, it's subject to your security settings. This is why "sharing" creates such huge problems for those in the industry - they are expected to have examples of their work on-line but doing so publicly makes it so naive or unscrupulous people, use their images without permission or financially compensating the photographer. These terms protect FB from being sued if and when that happens - which is more often than you think.

By creating a private secret group, which is not visible to non-members, the content is not publicly visible for sharing. By not tagging parents in images, then it doesn't filter into their own accounts where their friends can see it, share it, etc.

The only way on FB to create a truly private group is as stated. Any other way would allow people to search and find the group, read the content but not add to it.