Talk with your children frequently, and give them love, attention and discipline. Especially do not let them get away with things they would not otherwise. Children feel more secure with consistent rules, and when they know that the adults are in charge.
Make sure your children know how to reach your ex when they need to. And help them to maintain contact with other family members on both sides. It is all very hard work, but when your children know that things are going to be okay, they will do just fine all their lives.
All the best,
Chris