Teaching children can be easy if you tap into what they like to do and not force them to learn through boring methods.
Children like to play and you will be amazed at how quickly a child will learn vocbulary when they have to use it to get or do something they want.
Play games with children. There are so many games that can be adapted to the ESL setting like "Simon Says". In just half an hour, children will have learnt to recognise (not necessarily be able to say) the words sit, stand, jump, sleep, run, walk and turn.
This game can also be used to learn parts of the body. If you pre-teach the word "touch" then you can use the Simon Says game to teach children some body parts vocabulary combined with the word "touch". For eg: You could say "Simon Says touch your nose".