If you haven't been given a reading list like factor suggested ask your tutor for one or go to the library and explain what your assignment is and they will be able to help you find some information either in books or online. In the meantime some text books which might be useful for you-- Janet Moyles- The Excellence of Play, Tassoni and Beith- Diploma Childcare and Education, Tina Bruce- lots of books by her which might be useful.
http://www.ehow.com/a...ldhood-education.html this website gives a VERY brief overview of main theories on play but they date back to Freud which is obviously not current.
A big thing in early education at the moment is using the environment to help children play and develop; especially outside, you might like to look at Forest Schools for this.