I saw a post here and thought it was worthing mentioning.
The NASA Website has a great tool to help kids explore the solar system. http://solarsystem.nasa.gov/index.cfm?Display=Flash
It is all flash based, so it should grab the attention of students. It start with the Sun, covers all the planets, and even includes asteroids and comets. Each stop on the Explorer just has a quick overview, so it won't overwhelm younger visitors. The real magic happens when you follow the about link. There you will find a slightly longer overview, information about the planets moons, an extensive gallery, facts and figures, and a Kids Eye View (which is where I learned I only weigh 77 lbs on Mars).
This is just begging for a webquest.
Don't stop there, the NASA website has a lot more to explore. More pictures, more videos, more interactives, and even some downloads.