long layover at beijing airport

We have a long layover at the beijing airport on our way to the Philippines in october. From 5:30 am to 8:00 pm. We would like to leave the airport and do a tour of beijing. We are all us citizens. We all have passports. Do we need to do anything else? Will the 72 hr visa policy apply to us? Any suggestions on who to call to find out?

Thank you so much for any help!!