feedback on e4k stories

We are working on the Engineering4Kids wiki of engineering topics for middle school kids to browse and search. Very much a work in progress.
http://engineering4kids.wikispaces.com

We would love to get your feedback.

Engineering – Are there any obvious mistakes? What are important concepts we need to be sure to include? Suggestions for other objects that have good stories and/or demonstrate important engineering concepts?

Teaching, working with kids – We want this to be a resource for kids – targeting middle school (grades 6-8). We expect they will “search” for topics of interest. What makes a compelling story? How much actual information needs to be in the story? Most of the “stories” are summaries of information from other more in-depth articles.

We are planning to include kid-directed activities for each story. Would kids be put off if the activities were class lesson plans, rather than instructions directed to do it yourself?