I've also decided to get the Penguin cups & balls, & Carl Andrew Table Hopping Cups & Balls. Are the kids able to see cups & balls at a show.
(From my experience) Young kids don't fully understand some aspects of the cups & balls. Having said that, you still get a good reaction with the surprise ending. But for the most part they don't understand!
If you have a fairly easy to understand routine and something they can follow it should go down ok. Another idea is to add a story to your routine, this would make it more interesting and easier to follow.
Carl Andrews - Table hopping cups & balls.
In this DVD Carl teaches his Cups & Balls and sponge ball routine. I don't think either of these routines are suitable for kids and therefore don't recommend this DVD. (the routines are for adults) What you learn is a routine, not the principal of the cups and balls.
(Example: If I want to play the piano should I learn a tune or should I learn the keys? If I learn a tune I will be able to play that one tune, but if I learn the keys I will be able to play many tunes).
Do you see what I mean? The same goes for magic, if you learn the fundamentals you can do many routines (even create your own) if you learn a routine you can do just that one routine.
If you want to perform cups & balls get something like: Michael Ammar - Cups & Balls. This will go through most of the fundamentals and a few routines!