Then, another teacher at my school offered to do an awesome activity with my class. She found it here: http://www.noao.edu/education/peppercorn/pcmain.html
Here's what you need to represent each planet:
The Sun = A bowling ball
Mercury = A pin head
Venus = A peppercorn
Earth = A peppercorn
Mars = A pinhead
Jupiter = A chestnut or pecan
Saturn = A hazelnut or acorn
Uranus = A peanut or coffeebean
Neptune = A peanut or coffeebean
Most can be found at the grocery store or already in your kitchen. The hard part is creating the model. You need A LOT of space! We went into the fields behind our school on Monday because the weather was finally awesome. To get to each planet, you need to "pace" out your steps. For example, once we placed the bowling ball as the sun, we had to take 10 paces to get to Mercury. Here is a list of the distance between planets.
Mercury = 10 yards (or paces)
Venus = 9 more paces
Earth = 7 more paces
Mars = 14 more paces
Jupiter = 95 more paces
Saturn = 112 more paces
Uranus = 249 more paces
Neptune = 242 final paces
After we counted out the distance, we place a card with the "planet" on the grass.
If you teach the solar system, I HIGHLY recommend this activity!