The solubility of CO2 in alcohol/water mixtures depends on the amount of alcohol and the temperature. The solubility increases as the temperature drops (as with most gases). For low alcohol concentrations the solubility decreases as the alcohol concentration but for concentrations at about 10% and above, the solubility increases with the concentration of alcohol. For example at 20 degrees C, the solubility of CO2 for 10% alcohol is 1.23 g/L and for 12% is 1.33 g/L. So the pressure should go down as the alcohol content increases in this regime.