Mac Sierra, iCloud > Notes is greyed out
Solution 1:
I launched reminders and clicked reminders->add account from the menu. I logged in with the same iTunes account that is already setup in System Preferences->Internet Accounts.
Reminders and System Preferences crashed, but then I could see reminders and notes selected in System Preferences->iCloud. I can now see notes and reminders across my Mac and iPhone.
The options in System Preferences->iCloud are still greyed out.