iPad calendar only sees 2 of 4 GMail calendars, what have I configured wrong?
You can set up a CalDAV account to sync all your Google calendars. The following information is provided by Google and can be found here:

To sync with your device, follow these steps:

Open the Settings application on your device's home screen.
Open Mail, Contacts, Calendars.
Select Add Account...
Select Other.
Select Add CalDAV Account.
Enter your account information: 

In the Server field, enter [ google.com ]
In the Username field, enter your full Google Account or Google Apps email address.
In the Password field, enter your Google Account or Google Apps password.
In the Description field, enter the name you'd like to appear on the account.


Select Next at the top of your screen.

After you've completed setup, open the Calendar app on your device and syncing will automatically begin.
By default only your primary calendar will be synced to your device. You can sync additional calendars by visiting the following page from any web browser:

https://www.google.com/calendar/iphoneselect
(Google Apps users can go to https://www.google.com/calendar/hosted/your_domain/iphoneselect, replacing 'your_domain' with your actual domain name.)

Select the calendars you'd like to sync, and click Save. The selected calendars will display on your device at the time of the next sync.