I just love the name of these cookies! That seems like a lot of vinegar to me, though. I've always used 1 Tbsp for a quart.

Also, for the icing, it's a lot safer to use the refrigerated egg substitute or egg whites from the dairy case in place of raw eggs. Egg Beaters and their ilk are all pasteurized, unlike real eggs. The package will tell you how much is equivalent to one egg.