Talk to your friend. If it was me or a lot of the people i hang around with it would be no problem, you could drink or not it would make no difference at all.
But there are a tonne of recovering alcoholics out there who would **** themselves at the thought of a night like you describe so find out which one your friend is before they commit.
Good question to ask, as we discussed in another thread, is does he/she ever think about drinking anymore and does he/she have to avoid places that server alcohol? If you get a yes to this or anything other than a firm no then dont put them in the bar scenerio.
Actually now i have written the last paragraph none of this should be your problem at all, i know you are being kind but it's not like you are childminding and looking after a child with a peanut allergy and frightened if they go somewhere with you they might end up eating a peanut. I assume we are talking about an adult so throw it out there and then see if they want to come, you shouldnt really need to change your plans to accommodate this unless you are doing so because it is just you and your friend going?
Anyways make sure you have fun:-)