Can you tell us a bit more about the court orders? did they specify anything about what happens in the event that you go OS for military service?
Ok so this is a bit messy... But my understanding is that the primary carer has the responsibility to follow the orders. So for illuminations sake, orders say dad has the kids every second weekend. The courts cant force him to be at the designated location to pick the kids up. But the courts do expect the primary carer to follow the orders. So the court will ask, is there a reasonable explanation as to why you didn't follow the orders and now want them followed. The answer is YES... Does the ex have a good excuse for not following them now your back home? Don't think so... not based on what you've posted.
Mate go see a solicitor, get paperwork filed for a contravention. That means you can by-pass mediation. Sure you could do the paperwork yourself, but there seems to be a bit of urgency for you, so pay the money instead of filing yourself, making a mistake and having the paperwork bouncing around until you get it right... I like to encourage people who feel confident enough to self represent, but I reckon you'll get a better result faster with a solicitor....