I believe  you don �t need to teach rules first because it �s almost impossible for young learners to  understand them. Try to speak, using simple sentences and only when they get used to use them in their speech you may explain grammar in a very easy way. Sometimes I say, "These English are very interesting people. When we say something this way they say it in another way. Let �s remember and train it". I do a lot of presentations for them to watch and touch and choose and say. Good luck.