Create talking avatars for free, which you can embed and use to improve your message, improve comprehension and motivate recipients, as well as a test-to-speech tool.
Voki is a lot of fun. (You can embed finished Voki projects in Wikispaces, too, which could be very handy, especially if you're trying to create a simple site that would be engaging for kids.)
There are many types of cognitive and learning disabilities and an even wider variety of interests and capabilities of users who have these disabilities.This population is larger than those with all other physical and sensory disabilities combined. Cognitive accessibility can be defined by the following principles: Simple, Consistent, Clear, Multi-modal, Error-tolerant, Attention-focusing. Improving web accessibility for this audience will improve access for everyone.