Who doesn't like wiggly eyes? They are inexpensive and fun! Some might also call them googly eyes. Pick up a few packs of them and give them to your kids to play with. Please note that younger children need to be supervised because they eyes can be a choking hazard.
You can find these eyes at any local art store or even stores like K-Mart. They come in many sizes ranging from really small eyes to large 1.5 inch eyes. You'll also need paper, construction paper, pencils, crayons, markers, feathers, pom-poms, glue, tape, paint, paintbrushes, scissors or any other art supplies you might have laying around the house.
Lay out the supplies and gather the kids. Ask them if they would like to draw their own picture or if they are smaller, you can draw a picture for them and they can add the eyes. For older kids, just let them do it all themselves. They can glue or tape the eyes in place. Instruct them to draw people or animals.
You can even go around the house and outside to gather other objects to glue or tape eyes onto such as rocks, sticks, mugs, etc.
Let the kids rule the show and allow them come up with their own ideas. Encourage their creativity and when you are done, compare projects and praise each child on their amazing work.