Ordering by size.
The Black Hole Game (also free from NASA) was a hit with the kids.
We did some more experiments from Janice VanCleave's Astronomy For Every Kid,
. . . built models of the International Space Station,
. . . made paper space shuttles,
. . . and ate an astronaut snack.
Along with the usual lapbooking pieces, we used this one for animals in space.
Some additional links, the last one is especially good.
Black Hole Gravity Lens