How to salvage dry cookies

*While not answering the current question, this might be useful for the future: The way I reduce sugar while keeping the moistness during baking is to add more molasses and way less white sugar (using white is easier to control), keeping the molasses content *almost* the same with the original one.
E.g.: 2/3-ing 1 cup dark brown sugar (which has 1/4 cup=4tbps molasses http://www.eatbydate.com/substitutions/sugar-substitutes/) == 2/3 cup of total sugar, or ~10 2/3 tbsp == ~3 2/3 (or 3 1/2) tbps molasses + 7 tbsp sugar.
Note that that I didn't add the full amount of brown sugar to compensate for the reduce in total volume.

I like Sam's idea, too. Egg whites are drying so adding extra will only make the cookies dryer. (You'd be better off adding butter.) Also, I'm sure you reduced the sugar with the best of intentions, but brown sugar also adds moistness. It happens. ( I just made a big batch of bark in which the caramel didn't set up properly. ) Since they're for gifts, it would be best to try another recipe (and follow it exactly).

So sorry, but without seeing all the ingredients, I can't honest help. In truth, I've not always found his recipes to work all that well. His caramel recipe is worthless. Crystallizes every time.

Did you accidentally use too much flour? The recipe I looked at called for one and three quarter Ounces of flour - if you misread that as cups that could be the problem. To answer your question, no, I don't think adding whipped egg whites will help. I like Sam's idea of making crumbs - I bet bourbon balls made with the crumbs would be great.

Throw them in a food processor and use as a crust for a chocolate mint cheese cake.

Then make some fudge or rice krispy treats for the gifts. :)