The scope, style and professionalism needed for children's stage production depends upon the setting, style, age level of participants and local. Some types of productions, such as "Our Town" lend themselves to minimalist props or even to using imagination and pantomime. Whether you are setting up a family production for weekend entertainment or staging a community theater event, some things hold true in every case. Other things will change with the setting, scope and budget available for the production.
You can make backdrops from canvas stretched over a wooden frame, which, the industry calls a flat. You can join flats together to create a complete wall, or you can equip them with a hinged brace to stand on their own. If you paint the canvas, with a flat, water-based wall paint, you can wash it off so you can use it again for a different production. If you have a low or non-existent budget, you can substitute large cardboard boxes. You can use smaller boxes to brace larger ones or to hold up sections of background. Refrigerator boxes that are painted, decorated and weighted on the bottom make quick, easy to assemble buildings, trees and other backdrop items. Packing companies are also a good source for large cardboard cartons that you can paint, and turn them into structures for your set. If the production is a home entertainment event, the boxes then become play objects.
Furnishings, Forests and Water
Local furniture stores might be willing to lend appropriate furniture in return for advertising. If this is not an option, items such as couches, tables and similar usable items can be simulated by using folding chairs and tables or even classroom desks. You can lay a roll of blue-colored cloth across the stage to simulate water. To make waves, place the cloth in front of the actors, and have a stagehand on each side of the stage wave it up and down, to give the appearance of motion in the water. Take the centers from large spools of paper that publishing houses use to attach to a base to create trees. Attach cardboard "limbs" and construction paper "leaves" to the rolls.
Good Old Paper Mache
If your play calls for a rock, a mushroom or some other irregular shape, nothing beats paper mache spread over a poultry-netting framework. If your group has a parent that is handy with wood and nails, ask them to create a wood framework, with a solid support area if actors will need to stand on it. Bend the poultry netting into the desired shape, whether it is a rock or a dragon, and staple it to the framework. Make up a heavy-duty paper mache mix of one part flour or wallpaper paste powder, 2 parts water and about a cup of white glue per gallon of liquid mix. You can add 1/4 cup salt and some wintergreen flavoring to keep the mix from molding. Dip torn newspaper in the mixture and spread it in successive layers over the netting. When it is several layers think, paint it appropriately.
The items that actors carry about and use on stage can come from a variety of sources. Ordinary household items can be real objects if they are not breakable. Items that will be "broken" on stage should be pre-broken in advance so that the break is predictable. For example, to break a vase, use some ceramic green ware. Break the vase, and then glue it back together using light paper strips over the breaks. Do not glue the breaks, as a glued join is often stronger than the material. When tapped or dropped, the vase will then break into the pre-broken pieces. Use an off stage sound effect to make an exciting noise when it happens.