I would say its not safe. On top of the double downer effect of the benzos and the alcohol potentiating each other, the cocaine with the alcohol will metabolize in your liver so that cocaethylene is formed. Cocaethylene and cocaine together increases the stress on your heart, because now you have two stimulants in your body.
if youre trying to sleep, why bother with coke? Or alcohol for that matter. Alcohol can knock you out but it decreases sleep quality and you wake up feeling like crap between that and the hangover. If I was trying to be as safe as possible in your situation, and do what makes the most sense just for sleep anyway, Id just stick to the clonazepam.