Tie-dying is not only a fun activity for kids and parents, it can be a way to save old stained clothing from the rag-bag. No need to buy new t-shirts for this, just look in your own child's closet for articles of clothing that may be stained or in need of perking up. If you don't have any, don't make tracks to get a new t-shirt yet. thrift stores and garage sales are another great source for tees and sweats that can be tie-dyed. If it has stains, don't worry. The dye will cover them up. Just look for cotton garments in light, solid colors.
T-shirt in white or another light color
Fabric Dye (like RIT)
Create a design by tying your t-shirt with rubber bands (see idea links below). Place in a bucket with dye until the desired color. The longer you leave it, the more intense the color will be. Remove from dye and rinse with cold water until water run clear. Be sure to wash your t-shirt separately to avoid getting dye on any other clothing.