Display imported Google calendars on iPhone
Make sure you open all the links on iPhone:
1. Enable all the calendars you need at https://www.google.com/
2. From iPhone , goto Settings -> Mail -> Gmail Exchange -> disabled then re-enabled Calendars.
3. Then goto https://m.google.com/
sync/settings/iconfig/welcome? source=mobileproducts&hl=en , where you can select device and additional calendars.
4. Once you open up your Calendar application, you should be able to see all your imported calendars!