Mail by December 4th for guaranteed delivery.
Priority mail boxes (available free from the post office) cost $8.95 to mail, regardless of weight
Do not send rum balls. Nothing alcoholic is allowed is Islamic countries. The same thing applies to anything pornographic.
Keep in mind that although they may be sitting still at their base for the moment, they could be moved next week, which means 2 duffle bags, leave everything else behind. Any non-commestible should be small and something you don't care if it stays in Iraq.
The most valued thing to a soldier is to remember he is loved and missed at home. Even if there is nothing you wish to send in a package, send a card and if you can, include a picture. It's a touch point with a place they wish they could be.