Look up treasure baskets. They are a sensory activity geared towards infants and upwards and they are a great activity to do with mixed age groups as they get many different things from the experience. It is not an activity you should involve yourself in. Provide them with the treasure basket, basket or box and contents, in the centre of the room, and then sit on the outskirts of the room and observe. There are lots of great sites including different themed baskets and also google "how to use a treasure basket" so that it is used to its fullest purpose and intention. I just love treasure baskets!