Sand and Water Table
Set up a sand and water table for children between 2 and 4 years old. While kids this age may not be able to understand or participate in some of the more complicated messy play activities, they will love the experience of playing in sand and water, and exploring what happens when you combine the two substances. Dress the children in clothes that can get messy and, if the weather is warm, set the sand and water table up outdoors to avoid any cleanup.
Pudding Painting
For this activity suggested on the Kids Craft Zone website, whisk a box of instant chocolate pudding and 2 cups of cold water together in a bowl for approximately two minutes. Lay down newspaper to protect the workspace, such as a table, or even the floor, and set out large sheets of wax paper. Children will love using paintbrushes or their fingers to paint with the chocolate pudding, and you don't have to worry about young kids eating the paint.
T-Shirt Painting
In a great messy play activity for summer suggested by the Disney Family Fun website, hang one pre-washed, white T-shirt per child on an outdoor clothesline, away from anything you do not wish to get paint on. Dress the children in swimsuits or old, ratty clothes and provide them with paintbrushes and fabric paints poured onto aluminum pie or paper plates. The kids will have a ball dipping their paintbrushes into the fabric paint and flicking the paint onto the T-shirts. Allow the paint to dry and wait a minimum of three days before washing the masterpieces.
Spray Paint Mural
The Disney Family Fun website also suggests hanging an old bed sheet from a clothesline and filling spray bottles with a mixture of warm water and enough liquid tempera paint to add color. Set up one spray bottle for each paint color and set the nozzles so that the liquid sprays in thin streams. Set the kids loose in the yard and let them go wild creating their own personalized mural with the liquid paint. Be sure to situate the bed sheet far away from anything you do not wish the kids to decorate.