Are you using one of the 3A PiDrive power supplies and their split power cable that directly supplies the drive?
If so, you should be okay to use an unpowered hub to combine a wire keyboard/mouse onto one USB port.
I guess that makes
- Hub -> Keyboard + Mouse
- Screen power
- Picade PCB
- PiDrive USB connection
Don't try to combine screen, Picade PCB or PiDrive onto a hub without a powered one, though!