Decorate shoes - Buy the kids a white pair of shoes (not expensive) like the canvas type shoes. Provide them with glitter, fluffy balls, textas, stickers and other decorative craft stuff to decorate the shoes. Make them their "play shoes" which they can wear while playing.
Shoe box fun - Get an old shoe box, and let the kids decorate it and turn it into a scene. Turn it on its side, cut out paper people and animals and blu-tac them to the floor of the box. Assign a different scene to each child, such as ocean or jungle. They can also decorate the shoe box to be a storage box for their cards, jewellery, or small toys.
Poster making - Buy a large sheet of paper, and get the kids to each decorate their own to stick up on their bedroom walls. Get them to draw favourite TV show characters, favourite animals, or whatever they can imagine.