[cut, pasted and expanded from comment below]
Introduce myself - explain that I'm a teacher, that I'm from x church, that I love teaching their kids
Outline my program for the year
Give them a sample lesson - tell them a story from bible. (maybe)
Explain some of the [side] benefits of having kids in the program - better understanding of English literature, history, culture etc.
Talk about how RE helps kids
1. It gives them a better understanding of themselves - they are valuable and loved by God, they (like all of us) make bad choices, do the wrong thing and hurt others. They feel guilt (some quite acutely). Knowing what to do with guilt is really important. In RE we talk a lot about forgiveness and the God who knows everything that we think and do (both the good and bad stuff), who takes our actions very seriously but continues to love us.
2. Helps with fears. There is someone who is holding everything together. The overall narrative is under control. There are painful things along the way but these aren't the last word.
3. Gives hope - life after death.
Common questions kids ask.
Which bible to choose
What do you think? How would you do it?