If they have their own iPhones/iPads and use mobile Safari, 1Blocker is great for blocking ads and adult sites, and for other white- and black-listing on Safari

If they have their own iPhones/iPads and use mobile Safari, 1Blocker is great for blocking ads and adult sites, and for other white- and black-listing on Safari. It won’t work if your kids install and use another browser on the device (iCab, Firefox, etc.), but I suppose you could lock down app installations on whatever iCloud account is set up on the device (or with Parental Controls). The subscription is fairly inexpensive and the app’s blacklists are updated regularly. As a bonus, it blocks in-app tracking. (No affiliation, just a happy user.)