Privacy is a design decision, not a setting you find later.
Sort your content into three piles: public, signed-in family or customers, and administrators only.
Be conservative with anything sensitive—health notes, children's photographs, addresses, financial detail. If in doubt, keep it behind a sign-in.
Make sure you personally can still get your content out. An archive you cannot export is a hostage.
Practice
Write your three piles down before you invite a single person in.
Try this
Sign out and visit your own site. Anything you can still see is public.