Scoop.it recommended a good article from Smashing Magazine today:

A Dad’s Plea To Developers Of iPad Apps For Children By Rian van der Merwe.

Van der Merwe’s top four tips:

Affordance: Indicate where the interactivity is
Pagination: Page controls should be near the top of the screen
Menu: Should be a secondary action to avoid exiting the app accidentally
In-app Purchases: Don’t trick kids into buying stuff.  That ain’t cool.