As a lucky father who's son just returned after 15 months, I feel your pain and deep concern.
While it is no use to tell you not to worry, you naturely will. Try to find happiness in the fact that you and your family are committed to doing the right thing and seeing that freedom is kept alive.
While both my wife and I are military retirees we too found it very hard but supported the effort. Ou son returned a much smarter man though humbled too. Your children are embarking on a jouney that will forever change their hearts and minds. They will need and seek your support and knowledge while there, ever chance they get.
We, America, salute you and them. May they return in good heatlh with Godspeed.
Check out : http://www.bluestarmothers.org/
to see how others are dealing with this too.