Cut out a piece of stiff card in the shape of a rocket/plane/monkey/lizard and get the Beavers to decorate colour the card. On the reverse of the card tape two short pieces of straw. Thread a length of string through the straws to form a loop at the top and knot off the ends. Tape a coin or suitable weight to the bottow of the card to allow the card to drop when released. Now hook the loop of string over a door handle or coat hook and pull the strings apart, the card design will shoot up the strings and drop back down when the strings are loosed.
Card, string, colouring materials, coins, tape, plastic straws