Re: Convenience
You think Amazon can't tell the difference between voices on your account and create separate dossiers for each, eventually assigning them names (and the names of their friends, cross-referencing same), preferences, and who knows what else for each?
Note that on top of this, Amazon can (and does) follow your IP address as they/you pass through any and all web sites that use AWS. This is cross-referenced with the data you helpfully provide through your Alexa-thingy.
It's a multi-billion dollar international advertising corporation. That's what it DOES. If Amazon were human, it would be jailed for stalking. And you are not only enabling it, you are actively helping it invade the privacy of your children, before they have a choice in the matter.