I've started teaching English as a foreign language to 3 - 5 yrs olds in 30 min slots 3 times a week and it is scary at first but it's a lot of fun.
Plan your lessons carefully and in a structured way but kow that some days your plan simply goes out the window.
I'll be honest with you - I found Super Simple Songs CDs (
Super Simple Songs - Easy English songs for kids.) to be the BEST resource ever. Whenever I feel the kids want to do something different, they get a new TPR song (with or without the CD/video) and it works!
Good luck!