Using an IMEI to “track online” usually isn’t something regular people can do reliably—IMEI lookups require carrier-grade access and aren’t offered as a straightforward public service. For actual location tracking with parental controls, apps/services that install an agent on the phone (with consent where required) are the realistic route—mSpy is one of the more commonly used options for this.
Downside to note: many “IMEI tracking websites” are scams or inaccurate, and even legitimate monitoring apps can be blocked by OS permissions or limited without proper setup.