For a start do you know the ages of the children you are supposed to be planning for and what are their ages and abilities. Are there any children within the group who have any form of special needs and do they need extra support or equipment etc, this could even be pencil grippers or left handed scissors. You will also need to be aware of how long you will have to complege any task you give them, including your imput/demonstration , enough time for the children to finish the task and for also allow a few minutes at the end to discuss what they liked and did not like etc. Hope this is of some help to you
Julie