WH, I know it's scary and frustrating...however, you've done all you can for the moment. You've contacted your lawyer and the GAL is being made aware of it. That's all you can do. Trying to speak to your h isn't going to get you anywhere. Document the incident and when you have the children again, sit them down and have a talk w/them about what happened and especially talk to your daughter about the dangers of running away can possibly do to her.
Your h is not going to listen to you...but he will have to listen to the authorities when this comes up in the very near future.
Breathe! Your children are now safe and back home.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.