While nothing beats the look and feel of natural clay, most of us don't have easy access to a kiln. Super Sculpey is a nice alternative. When I worked at Disney, I sculpted Maquettes on my lunch breaks with the uber talented Kenny Thompkins. We used Super Sculpey to create the maquettes. Sculpey is awesome because it doesn't dry out or require special tools or glaze. When you're ready to finish your Sculpey project, you simply bake it in your oven, sand it with sand paper (if necessary), and paint it with acrylic paint.
Here is a maquette I made of Mr. Smee. I started with a wire base and attached bits of clay to the wire. Kenny taught me to focus on building the basic shapes (mostly spheres and cylinders) and to worry about the details at the end.
Your kids can use Sculpey to sculpt little statues like this. It can also be used to make beads, bracelets, and other objects like cars, animals, model buildings...whatever your children are interested in. Let them do their thing with the clay, pop their creations in the oven, and give them some acrylic paint to finish them off! It's a nice material to have on hand in your home or school art studio. It doesn't dry on it's own, so you can leave works in progress out for as long as you'd like. This allows kids to take their time on projects and revisit them over several days, weeks, or even months.