Travel to Auckland in December and back in January, both via Beijing

Hello,
we will travel with my husband to Auckland in December 2017 and back from Auckland in January 2018, both journeys via Beijing, where we will stop for approx. 12 hours each journey between the flights. We have the passport from the 24 Schengen Angreement Countries. To get the Direct Transit on both ways, what do we need to prepare in advance? Is it OK, if my passport is valid until the end of May 2018 (I am supposed to have the transfer via Beijing in January 2018 on our journey back)?

Thank you and best regards!

Gabriela