Collect and retain only the minimum personal data needed for each element of the service the child is actively and knowingly using: map the data and retention needed per element, give children separate choices for each optional or personalising element rather than bundling them with the core service or with each other, and collect data only while the child is engaged with that element (for example no location tracking after a map is closed).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.