Cut squares and have them draw their favourite picture using Crayola crayons. Iron to set the colour and stitch the squares together for a camp banner or table cloth. Make sure the squares for the background are poly/cotton as the wax does not adhere to the pure cotton nearly as well. It's remarkable how well the colour sets into the fabric and it can be washed in cool water without losing its vibrancy. I've made classroom quilts using this technique and they've been great and been lasting memories for years. If you didn't want a large banner you could have each square made into a mini banner for the kids to take home. It would just be a matter of elongating your starting piece of fabric to leave enough room to make a small casing at the top and inserting a piece of dowling so it could be hung. Happy creating!