Delete TikTok. Done. They don’t need it. All that app does is fry their attention span anyway and expose them to trends that are honestly pretty stupid and sometimes dangerous.
If you absolutely must let them have it, then yeah you need monitoring software. But don’t kid yourself that you can just set some limits and walk away. You need to actually look at what they are watching because TikTok’s algorithm will serve up literally anything if it thinks it’ll keep them scrolling.