Your machine configuration should be ok. The problem with two fire wire cameras is that they interfere with each other when connected to the same fire wire bus. Even if you happen to have two ports on your computer it is most common that they are on the same bus. Unfortunately the MacBooks-Pros-Retina don’t have any Firewire bus at all. You will need a 3rd party hardware to connect your firewire cams to your thunderbolt port.
I use two thunderbolt to firewire adapters on the 2 ports thunderbolt with my MBP.
I just make a very short test with two cams (Sony DCR-HC62E + Canon xl1s) without problem.
I like your advice because I prepare from april many webTV news with students on an educational project.
Thanks