I think you answered your own question.

After i get the value of the voltage divider, can i "quick a dirty" multiply the current value with two in my code?

Generaly it will works.But actual integrated circuit are never equivalent to a perfect voltage source. There is allway a parasistic serial resistor (Rs) inside the IC.Generaly this parasistic resistor is very small but by security I would have a look on the datasheet.If Rs = 1 ohm it will not affect the calibration of the voltage divisor, but if Rs = 2 kohms the top resistance will be equivalent to 2k + 5k ohms and the ratio of the voltage divisor will be modified. R= 5( 2+5 +5)= 0.416.