Group Guangdong visa for a group of 10 from the Philippines

We are a group of 10 from Philippines. We would like to enter the Pearl River Delta Region (Shenzhen and Zhuhai) from Hong Kong on May 3, 2012. How do we apply for a group visa? Is an organized tour necessary? Because we prefer to explore the region on our own. Can you recommend to us reputable travel agencies who can process group visa for us? Thank you!