Students may avoid someone else's ball from hitting their feet by jumping, sliding, etc. Older students can use the overhand throwing motion. Have students throw with their non-dominant hand. This makes for a good conversation after the activity is over. Take resting pulse before and after activity to see how this activity raises heart rate.
Students have a tendency to run after stray balls with their head down.
Make sure your students have a good grasp on moving in general space with others in a dynamic setting. Start the activity off by walking. Then change to more difficult locomotor movements as you are satisfied with safety.