We are intending to build a website for evaluating kids (games, quiz). What are the specific interface recommendations for focusing on the children (e.g. keyboard usage inside a laptop or perhaps a stand alone keyboard, capability to control a mouse, capability to navigate the interface and it is controls, size buttons, page navigation)? We're searching for things which we have to be cautious about.

Jakob Nielsen includes a pretty decent Alert Box about usability for kids. Gleam usability guide in the finish from the alert box. To sum up: kids don't scroll, that like reading through, are suckers to promote, and when Microsoft Bob was promoted to children, it would have been popular.