They do not need you to be friends. They need adult conflict somewhere they cannot hear it. Repeated hostile exchanges, even about logistics, can be distressing for children.
It can show up as stomachaches, sleep trouble, clinginess, aggression, or sudden quiet. Some kids try to referee. Some vanish into a screen. Those changes can have many causes. A pediatrician or qualified mental health professional can help if you are concerned.
Move hard talks offstage. Written messages. A call when kids are not in earshot. If a disagreement starts at exchange, table it. "We will discuss this later." Then actually discuss it later.
If they overhear something, repair simply. "That was an adult disagreement. You did not cause it. You do not have to fix it."
When kids must see a difference of opinion, model it without contempt. Calm tone. No insults. A clear pause. They learn more from how you disagree than from speeches about respect.
Frequent conflict calls for more structure: parallel parenting, shorter exchanges, third-party pickup spots when appropriate. Reduce the scenes they have to watch.
Protecting kids from adult conflict is not denying reality. It is choosing where reality gets processed.