If you boil the alcohol out I would imagine you would kill the very flavor you are going for. How much whiskey are you wanting to add here? I would just add it once fermentation is complete if you are set on it.
What flavor is it that you are after? Seems like a waste of whiskey. You may get what you are looking for by adding some heavy toasted oak.
I haven't flavored a wine, but I put rum essence in a Ginger Beer once and that worked great for a Dark N stormy taste without the alcohol.
If you still would like a whiskey flavor, then get an whiskey-essence and try 1bottle or so, then try a whole batch if it works out fine. Just my two cents