A recent BBC Tech article mentions police forces warning of the risks when posting school photos online, but this could also apply to a charity posting images of children generally, and so it is worth a read at https://www.bbc.co.uk/news/articles/cwyz6g2wx56o.
Perhaps it’s timely to review your photography and filing policy, and please remember that the ICO has a whole section on a Children’s Code and children’s online privacy at https://ico.org.uk/for-the-public/the-children-s-code-and-children-s-online-privacy/.