This was pretty easy and quick, and the kids loved it. You can find the directions here.
I am terrible at balling melons, so my race car was not very full because I had a lot of "waste" (which the kids ate while watching me work). On second thought, I should have added some more fruit, such as grapes or pineapple chunks.
One tip if you are going to make this: wait until your kitchen floors already need mopping, as they will definitely need cleaning when you get done with this messy, sticky project (and all the melon that will inevitably get dropped everywhere if you have kids eating).