Just need a different idea than the balloon. Wacky sacks are balloons filled with playdough. Keeps kids' hands busy while they focus on the teacher :). Can serve as a stress ball for teachers too! All directions are here along with pics.
raised salt painting: create design with glue, cover glue with table salt. Touch watercolor brush on salt, without smearing and watch color be absorbed by salt. Let dry. This looks fantastic. So, inverted rock salt painting.
Magic Milk Paint idea from Modern Parents Messy Kids. This is another one of those awesome 'science meets art' activities for children, and you only need milk, dishwash and food colouring to do it. Looks fun :)