I would choose the Activity set : The sun and shadows.
The children could start the lesson exploring their shadows on a sunny day and with a game of catch the shadow.
The children would then be given a torch and a toy animal to make shadows. They discover how to make their shadows bigger/smaller/fuzzy/clear. By moving the source of light what will happen the shadow? What colour is your shadow? Using different materials what creates the best shadow?
This lesson would then lead on to the children designing their own shadow puppet and making a short play in small groups.