This is from Minna no Nihongo Chapter 15. It's a description of Santa Claus. でも世界の子供はみんな私を知っています。 みんな seems like a counter of sorts (I don't know how else to describe it) for 世界の子供. I always thought ...
After reading @jkerian's comment in this post, I started thinking about this. Here's the comment in full: On a side note, all days ending in '4' are also irregular, and use ~よっか. So the 14th is ...