OneCare will never wake a computer to perform a backup or a tune-up. If you wish to automate this, you'll need to create a Windows Task Schedule item to perform another function, such as open notepad.exe at some point before your scheduled OneCare task and before it would go back to sleep on its own. As for the external drive also powering down, you'll need to check with the manufacturer about disabling that shut down or how to wake the drive when the PC wakes from sleep.
-steve