Designing websites for kids is a fascinating, challenging, rewarding, and exasperating experience: You’re trying to create a digital experience for people who lack the cognitive capacity to understand abstraction.
You’re trying to establish brand loyalty with people who are influenced almost exclusively by their peers. And you’re trying to communicate subjective value propositions to people who can only see things in black-and-white. Add to this the need to collect data from people with a deep-seated fear of sharing personal information, and you’ve got your work cut out for you. Let’s remember, too, that these people are still learning how to read, and haven’t taken Typing 101 yet.
Fortunately, it’s possible to create a successful registration process for these folks with an understanding of how their brains work. We’ll explore how to design effective registration forms for kids based on their context, technical skills, and cognitive capabilities.
Successful registration forms for kids:
have tangible value propositions instead of abstract activities,
provide opportunities for creativity,
use pictures whenever possible,
require little personal data,
and use “friendly” language...
http://www.alistapart.com/articles/designing-web-registration-forms-for-kids/