Time machine & Multiple hard drives

You need an external hard drive at least the size of your primary internal hard drive to use Time Machine.

 

A Quick answer would be no. Theres no way to send the backups to two different hard drives. Not automatically anyway. You can do it manually, but it will just backup to that drive until its full, then you would have to manually switch to another drive, and it will create a whole new backup(IE 1st backup very long backup).

Im in a similar situation. But What I plan on doing is moving my backups to one of the other drives, thus freeing up space, and then having TM re-backup to the same drive.