Is it really going to kill you to mute them? I mean seriously it is NOT that difficult. Unless you just enjoy whining and complaining about every little thing that doesn't go your way. :/
What I can't stand in regards to children on mics isn't their voices it's the people that have to type in the chat:
"OMG SHUT UP!"
"U CHILD U NEED TO SHUT UP."
If it bothers you THAT MUCH then maybe you should play with your sound off.
As Luvedragon pointed out they're just their to have fun like everyone else (unless they're obviously micspamming but that's when you get an admin's attention and tell them what's up).
And also as she pointed out:
squeaky/higher pitched voice =/= child
There are females on the internet, shocking news for someone like you I'm sure, but it's true.