One of the difficulties of setting up your Gmail account on your IOS device is the lack of push support when setup as a Gmail account. As some of you may know you can setup your Gmail account as an Exchange account, (directions here) which I recommend doing. Now that you have your exchange account you need to setup your multiple Google calendars.
Step one is to open Safari on your device and navigate to http://m.google.com/sync Click “Sign in with your Google Account”
Here you can login with your Google Apps information or your personal account information:
Next you will be presented with the devices that you have tied to your Google Account. Click on the device that you would like to configure.
Make your selections and than click “Save”
After you click save click on your calendar application on your device. When you do, you will see the calendars populate onto your device.
*Note: You can also navigate to : www.google.com/calendar/