I would recommend getting Celestia and letting them play around a bit with it. Any map to scale will show tiny dots separated by enormous distances. That is an important lesson. Players also need to get to know the overall "topology" of the solar system (the order of the planets and moons, how the giant planets got their own little solar systems of moons etc). Having something you can zoom and fly through is very useful.

http://solarsystem.nasa.gov/eyes/ this is an amazing accomplishment of humanity, it shows the real time locations of all the major celestial bodies and man made vehicles. the beta launched almost 2 months ago, and its FAR more stable since its release. the GUI is a little finicky, but its still nice. for my campaign, i chose to assume the solar system to be static, i chose to make these locations according to how the solar system was on May 8th, 1982 8:45 am. because the planets were fairly linear. this is a FANTASTIC model for players who demand a level of realism, without over complicating things to severely. it would take less than an hour to plot the relative distances of every planetary body from every other planetary body. which are REAL distances, with a level of accuracy that is actually sort of absurd. the REALLY nice thing is that if you zoom in, every moon and planet is textured with all the photography humanity has available. this will eventually expand to include neighboring star systems once it changes hands from the jet propulsion lab. (though it is powered by google)

I was hoping to find an image that shows all the major bodies in the system that are known, if indeed some brinkers or hypers are out in the oort cloud, I'd like more info on whats out there. Baring that, I may have to make my own...