If you are concerned about your kids using Alexa in your home you should read the article on this link. She has actual experience using it with her four kids and her husband helped develop Alexa. She suggests:
Turn on explicit filters for music services
Consider blocking drop-ins from outside your home
Turn off Alexa on any Kindle Fire tablets to prevent searching skills
Consider turning off voice profiles
Let me add, if you have a friend named Alexis you might forgo the "Alexa, play Here Comes Santa Claus," jokes.