I'm going to go against a few people here, but oh well...
You can't have a show until you build a show
You can't build a show until you know what works
You won't know what works if you don't get some experience
You can't get this experience if you don't perform
So, go out there and DO IT! Do as many free shows as you can, to as many people as you can get to watch you. You have a great opportunity to learn what works. Don't let it pass by simply because some people say you're not ready. OF COURSE you're not ready! That's why you NEED to do this show!
Yes, agreed. Of course, make sure you have appropriate tricks for these kids (the coloring book, egg vase, etc... stuff that is very simple and not/having to be expensive..... for five year olds, it should work). And have the proper presentation for it. Some study materials as others have suggested would be very benefit greatly.
But you need to perform some free shows when starting out. Get the feel of it and each show should teach you something.