A classic, time-tested activity is "Charades." This requires acting out a word, though the activity can be made more complex by having kids act out a phrase. The longer and more challenging the phrase, the more challenging it will be for the person performing it. Let the kids select their words from a basket of folded papers and phrases or draw "secret" envelopes in which their words are hidden. Use words from a play you may be rehearsing or from daily activities.
Have students form two lines that face each other. For each duo, one person is the "mirror" and the other is the person using it. The kids should put on makeup, try on hats, stare, make faces and gestures and so forth. The person assigned the role of mirror must try to accurately "reflect" what the other is doing. Do not let the children who are performing move too fast or it will be far too difficult for their "mirror" to keep up. Shift partners by moving one line after several minutes to give each child different faces to mimic. Then reverse the lines so that those who were using the mirror before become the mirror.
Some of Marceau's and other mimes' best work was done using the simplest of concepts. Let the kids try their hand by miming these scenarios: walking through an old western saloon door, leaning on a wall, walking down stairs and dancing with an imaginary person. Ask the children for ideas, too. Create improv scenes for them to act with a partner or in teams. Partners can create a mimed scene, such as two elders meeting in a park on a sunny day that changes to rain, being locked out of the house, receiving a gift, going fishing and so forth.
Have the kids make a large circle. Pretend to hand them an object, such as a large ball, a seashell, a rose or a 20-pound bag of potatoes. Try this two ways. The instructor or group leader mimes the shape, weight and size of the object, then passes it to the first child. Watch to see if the items changes as it goes around. After it has gone fully around, ask the kids what the object was. If they all guess it correctly, continue with an alternate approach; simply tell them what they are passing. The kids can pass the object to persons on either side or throw it to someone across the circle.