Both VM's should upgrade just fine - the first time you launch them, you'll be prompted to 'upgrade this virtual machine'. That'll upgrade the virtual hardware. VMWare tools inside the VM should automatically upgrade after boot, but if it doesn't, you can reinstall the tools from the menu.
There is a chance this will trigger windows re-activation - haven't done this big a jump personally, but something to be aware of. Just follow the prompts on the screen from Windows if it happens.
Absolutely on the backup. You can take one drive and partition it into two parts using disk utiltiy. I'd probably go with 500MB and 1.5 TB on a 2GB drive. CCC has a feature where it will preserve older files (and auto delete as needed) as a further fallback, so that'd give it some space for history. One of the VERY cool things about a CCC backup versus time machine is that you can actually boot directly from it - so you can keep working if your internal drive fails until you get it replaced. I actually use both CCC and Time Machine. Time Machine is my 'oops I didn't mean to delete that' backup (and it's really good for recovering email messages too - just have mail in the focus when you go to the TM icon). CCC is my 'bleep - the drive just failed' backup. :-)