T.T.
If this is his first time to leave for Iraq (first deployment) please please keep in mind that it may be WAY overwhelming to him to have allot of people around him when he gets home. My brother in law has been 3 times...his first time back he saw NO ONE. By his own request. He was trying to digest going and coming back and the whole reality that this is war...and family and...well, you get the idea. What I'm getting at is that if you plan a party, be prepared for that if it happens.
It is NOT however inappropriate to throw them a wedding reception if they were not able to have one before he left. I would word it something like a reception to celebrate their new life together and make sure you have them register so that they get the color/scheme they want (not the purple chicken aunt Mildred wanted her to have...lol) and you can also register for $10 gift cards (or $20) to help set them up as well.
Congratulations on your daughters wedding. And God speed to your new son in law's safe return.