I'm going to say the same thing I always say about mixing cocaine with alcohol; it's really not something you should be doing until/unless you have a very good understanding of how the respective substances affect you. The specific issue is that mixing cocaine with alcohol doesn't simply superimpose a cocaine high on drunkenness; instead, your liver synthesizes a longer-lasting, more cardiotoxic cousin of cocaine called cocaethylene.
Ordinarily, when you do coke your liver breaks it down into benzoylecgonine and an ecgonine methyl ester; both of these chemicals are inactive in the human body and basically harmless. However, if you drink and do coke at the same time, your liver winds up trying to process both the cocaine and the booze at once. In that case, your liver will react both the coke and the benzoylecgonine with the booze to produce cocaethylene instead. Cocaethylene is also a triple reuptake inhibitor (for serotonin, norepinephrine, and dopamine); it lasts much longer than cocaine does, it's harder on your heart, and it hits your brain's reward system (dopamine) just as hard as cocaine but with much less serotonin activity, making it more euphoric than coke. It won't necessarily kill you to have that stuff in your system in small amounts, but since the drug is actually produced in your liver you have only a very indirect control over the dose and thus need to be really careful. For a birthday party where you're considering engaging in all sorts of polypharmacy I'd be really careful about including cocaine in your list of things to do for the evening.
