For 4 to 6 year olds stories, make-believe and songs are the way to go.
I have a complete curriculum for that age group with games to teach the language, stories, songs to go with the stories, and masks to cut out and colour of the characters.
There are also all the vocabulary flashcards you need, plus story illustrations and for each story there are lesson plans.
Because it is a downloadable resource it is highly affordable. The songs can be sent by post if you prefer on a CD, or by download for immediate access.
To test it all out I give away a free mini-series from my site of pre-story games, the story, ideas for after the story and the matching song.
Do do check it out from this page: Preschool ESL: Games, activities and stories
Also for that age group plays and skits are fun and there is a free one of those on my plays page. You would use games from this website, or my preschool games book that comes with the stories to pre-teach the main vocabulary in the skit. You put it together gradually over a series of lessons, say ten minutes per lesson on the skit and the rest of the lesson doing other things such as vocabulary games, songs with actions, hearing a story, taking part in the story telling, and so on.
Once you get into it you will soon find out that teaching kids is WAY more fun than boring adults!