Find My iPhone doesn't notify the other device users that you're checking on a location unless you direct it to send an email when a missing device's location is found (if a device doesn't appear, due to bad signal, subway, etc.) You may passively track the location of all devices listed with Find My iPhone under the same Apple ID.
This comes in handy when you have several family members owning several devices each. If something is misplaced, lost or stolen, you have all of the device locations listed in one viewing app. Then you can lock, wipe, etc. as needed for security.
FMF is a better way to do this. Doesn't get into the whole email and iCloud thing. Of course the parent, IMO, should know the apple and iCloud id.