In the first phase, every civil servant must use (be affected by) the system, as well as politicians (including their families). Basically everyone who gets a salary or pension paid by normal citizens.
Also, every piece of software used by the government, or providers, which is related to this policy, must be open sourced, and attempts at finding security related issues or bugs in general by anyone must not be considered an illegal activity, but considered a helpful activity.
If they are ok with this for five years, and no unfixable problems or possibilities of misuse are found, then it can be applied to the rest of the population.
After all, one must assume that child predators are also among civil servants and politicians. It would enable the measurement of the success of this policy.