Writing for kids is so difficult. One problem is geting kids to sound enough like kids to be credible to them, the other is to make the copy entertaining enough for them to pay attention. Most industrial "kid speak" sounds patenlty fake and fails on the "interest" side too. (One good model for good kid copy I've heard recently are in the film "Mean Creek").
Kids don't typically write well for kids though. Instead, some of the brightest writers fo, those who have aknack and an ear for it.
I'm not Judy Blume, so what do I do?
I've found that listening to kids on the set is often helpful. Our brighter actors have good ideas for improving lines, and substituting words. Why not put a propoased kid-aimed piece in "workshop"--like the Broadway-bound plays do, to iron out the kinks and sharpen the edges? Hire a panel of kids to read through your script and do riffs on it in front of a DV camera. Let them improvise some scenes and come up with questions and suggestions about the proposed product/service/offering. It's a combination casting session and script session.