Children have limits. Children learn what we as parents teach them. If you lie to your child about the other parent, it will come back to haunt you. They will be able to figure it out on their own, if they've been lied to. None of their business- Parents have their own responsibilities.
Children are just that, children.
Kids have enough stress with school, homework, chores, friends, etc. These are all examples of P.A.S., but NOT the only examples.