I agree with those who say that if you have no idea, you should wait a while before you start teaching. For when you are ready to start, here are some ideas.
1. Remember back to what your teacher taught you in your first lessons. This is a good starting point.
2. Keep in mind that a lot of your technique will be automatic. Spend some time analysing your playing so that you know why you do what you do, and the reasons behind good technique, which is important from day one.
3. Most of the time, people's musical development is quite predictable. However, it takes time to learn to predict it, and you shouldn't rely on it. Have backup plans in case students move slower or faster than expected.
4. Please, for the love of God, DO NOT write the notes on the music. I have had endless headaches with students whose previous teachers have done this for them. They are capable players, but they have trouble moving forwards because they struggle with reading, and they know this themselves. Teach them strategies such as memorising certain notes (say, middle C) as "anchors" to work out other notes from, and how to read by interval. At most, give them a couple of finger numbers, or let them write in notes themselves (IN PENCIL!), but stress that these aids will be removed, and MAKE SURE you remove them within the timeframe specified.
5. As for fun: I can't think of any games for that age, but one thing that I've found is that most kids are fascinated by the inner workings of the piano, and showing them how the sound is made with the hammers on the strings can generate enough interest to keep them there and paying attention.