Definition: An ex parte decision is one decided by a judge without requiring all of the parties to the controversy to be present.
Ex parte is faster in that one party (in this case, one parent) files for relief, usually with some level of time or urgency. Typically, if approved, the court will later have a hearing where all parties can be present to present their respective cases.
So your lawyer's goal will probably be to present a case where the parenting or the child's welfare is compromised and addressing the issues are best done sooner than later.
The normal court process can take many months. My divorce was nearly 2 years. When I sought custody it took about 18 months. When I later sought majority time (only got it during the school years) it took about 18 months. Clearly, your lawyer's reasoning will be that the children and father can't wait a year or longer before the current situation is remedied.
One problem is that courts often don't grant all of a petitioner's requests, even if valid. For example, I requested majority time. The decision/order was that Mother had disparaged Father repeatedly. Yet the new order changed the equal time to only give me majority time during the school year. Summers remained equal. Why? Despite everything, the court was still reluctant to pull too much away from Mother.
Well, as I knew would happen, things didn't improve. Ex was still entitled and kept playing games with exchanges and other aspects of parenting. The next year I was back in court - again. It took about 17 months and more $$$ but the court accepted that me getting custody didn't stop my Ex's "continued disparagement of Father to the child". As a result, I gained majority time during the school year, "however, after considerable thought, this magistrate is willing to give Mother one more try... . Mother shall have {equal} summer parenting time". Yes, court lambasted her behaviors and still bent over backwards for her. When we first got our temp orders, I had 22% time with no dings against me except for being a working father (and she had a DV case pending against her which domestic court clearly ignored). Despite her poor behaviors in and out of court for 8 years, she has only been reduced to 25% during the school year. It's a 33% annual average if I include the 11 weeks of summer equal time.
(1) Court decisions generally are better, or at least seldom worse, than what a disordered spouse wants. A settlement seldom works until later in the divorce process when the demands become a little less unfair.
(2) This is where you have to get consequences built into the outcome next time in court. Courts are often willing to make a decision, it's much harder to get them to enforce them. That's why you need consequences built into a decision, that can reduce the endless "one more chance" that courts often declare when we report noncompliance.
What I'm thinking is that Father would do well to also ask for what he feels would really and truly fix the problem long term... . "Your Honor, I believe that our family circumstances require me to become the custodial parent, Residential Parent for school Purposes and Primary Parent with majority parenting schedule. Failing having custody, I believe that having Decision Making or Tie Breaker status with equal time would at least improve the current state of parenting and our children's welfare. Mother has demonstrated that she is unwilling to cooperate and share, something I can do as a reasonable involved parent. I am concerned that half-measures will be insufficient and the time spent on minor changes will continue enabling the other parent to further sabotage the relationship of the children with their Father... ." Of course, long term solutions aren't handled in an
ex parte filing but there shouldn't be any harm including it, though we're not lawyers here.
What that does is let the judge know father is not one willing to be a token father, he is stepping forward. Also, it presents to court that if the court's usual minimal changes don't work, then father will again return to court to state what would work and again ask for real solutions, not patches on an order that's not working.
My lawyer once explained to me one reason why courts are reluctant to make big changes to an order, "Courts don't want to upset the children." My response was, "What if NOT making big changes will upset the children?"