So often recipes will say not to double, or it will not turn out. I often wonder why. I think you should easily be able to double it, but double probably wouldnt' make 14x14. One solution is to mix it up three times, then bake it in one pan. That way you won't risk tripling all but one ingredient, hence messing up the entire recipe. Personally, I think I would try to triple it, what's the worse that can happen (you didn't want me to add that, did you?)
Good luck, and it sounds delishious!