I have a slightly more complex setup in that I have an AppleRAID-0, joined with an SSD which is my startup volume. It runs great now, but it was a pain to get it set-up.
If you're going to be wiping the drives anyway, then I recommend installing OS X onto one of them in order to create the Recovery Partition. If you like you could even copy that structure onto the second drive as well (or run the installer again, just keep a copy handy as it has a tendency to delete itself), as this gives you two Recovery Partitions, keeping you covered just like a RAID-1 should.
Then you can use the main partition of each disk to create your RAID-1, then convert that into your new Core Storage volume; unfortunately this will wipe it again, requiring a further installation to finish the process, but it shouldn't encounter any errors (unlike all the other methods I've tried). Once you've got OS X setup you just enable FileVault 2, run through the setup wizard and restart; if everything's gone smoothly then Core Storage will start encrypting everything in the background.
It seems a bit longwinded I know, but I've tried setting up the partitions and RAID first and the OS X installer just hates it; the really annoying thing is that it may even run through a big part of the installation before actually failing too, so I now prefer to do the single disk install first as that way it should definitely succeed, and you then know exactly how big the partitions on the other disk need to be, or can clone it whatever.
To answer your other question; yes FileVault is pretty easy to turn off, in fact if you run into any issues while setting it up for the first time it'll switch itself off if you power down your computer. One thing to keep in mind is that if you use a Bluetooth keyboard and mouse then you may need to connect a wired keyboard to enter your password for the first time, after that though your Bluetooth keyboard should work. It's also worth noting that because the FileVault login occurs before the OS starts up, some devices may not work at all; for example I find that my Logitech mouse won't work at all during FileVault login, though you only need the keyboard for that so it's no big deal, it also seems that some hubs may not work. I recommend you just try it and see, but if you find an input device won't work then you can try connecting it directly to your machine.
