Re: Teaching very (very) young kids
I would not try to teach a child of 18 months, I would play with the child, speaking English to it as naturally as I would to an English child of that age, sing nursery rhymes, and, with picture books, tell simple stories. I would, for 5-10 minutes watch episodes of children's programmes on YouTube with the child.
That's what I would do if I were asked to 'teach' a young child. It is what I have done with my honorary Czech grandson from the time he was born. I did not pressure him to speak English, but encouraged him to do so when he seemed to be interested. Now, at three and a half, I am putting a little pressure on - he knows that if he wants some šunkou a sýrem, for example, he won't get any unless he asks for ham and cheese.
He understood English almost as soon as he understood Czech, but did not really start to speak any until a couple of months ago. Now he is beginning to speak it more and more - not because he is learning a foreign language, but because he wants to communicate with me.
Context is always important; labelling is rarely important.