I agree with Mark and Simon, this is going to be a great adventure. When I started teaching English in Japan, I was kinda thrown into a situation with no training too. Fortunately for me, I was a music teacher back home, so I had a bit of teaching experience. I know many excellent English teachers though that have started from no experience at all.
If you can get a hold of Practical English Language Teaching: Young Learners by Caroline T. Linse, I would recommend it. It has a lot of great ideas for teaching children English.
Two children’s books I highly recommend: Brown Bear, Brown Bear by Bill Martin Jr. and Hungry Caterpillar by Eric Carle.
I don’t know if you will have a cd player there, but bring some music, especially for the younger kids. I have a bunch of free songs you can download that go great with the MES English Flashcards on my site: www.dreamenglish.com
All the songs have lesson and game ideas, so that could start you off.
If you won’t have a cd player, and you are so inclined, brush up on some childhood favorites, head, shoulders, knees and toes, London Bridge, etc. You can base a whole lesson off of one song.
Like everyone else said, have a great time, and if you learn some cool things about teaching English to kids, put a post back up on this forum so we can learn from you!
Kid's Videos for learning English! http://www.youtube.com/dreamenglishkids