When reading the descriptions of the I2C protocoll or some other two-wire interface that behaves like I2C in a random datasheet, one often has the impression to have discovered a totally new protocoll. The same thing is described differently, every time!
However, SCCB (serial camera control bus), Omnivision's I2C variant is different: the ACK bit (the 9th bit after each byte of data transmission) does not indicate ACK or NAK but is set at random -- the I2C master is supposed to ignore it.
The TCA6507 can cope with the 1.8 V from beagleboard's expansion header and the 5 V power supply.
There is a Linux driver for the TCA6507 (since 3.3), so you can control the LEDs nicely:
i2cset -f -y 2 0x45 0x02 0xff to turn on all LEDS to full brightness.