Mac Sierra, iCloud > Notes is greyed out
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.