Just to confirm what others have suggested, an ST-E2 (Canon or Yongnuo) or a 90EX will give you full manual or E-TTL II control of your two 270 EX II flashes, complete with ratio control, FEC and 1st/2nd curtain sync, all through your 5D II's flash menu.
The 90EX can be set so that it doesn't contribute to the exposure when used as the on-camera master.
Adam, how do you assign groups to the 270EX II's? On all other Canon flashes you have to do that on the flash, even when you control them via the camera, there is no way, that I can see, that you could assign one 90EX to group A and another to group B. Further, no Canon flashes do remote second curtain sync. Once you go to remote triggering you can't select it, you can do HSS in remote, but not second curtain sync.
You're right - my bad. I didn't take into account the 270EX II's lack of group selection. It's a pity as it would make it much more useful.