When you are a grand parent, unless standing in the shoes of a parent, you have NO RESPONSIBILITY. Bathe in it. Bathe in the fact that you can go outside and smell the roses while the family is screaming their guts out.
You don’t have any duties.
This grand child is climbing the wall, that grand child is making a mess, the other is screeching; you go outside and small the roses.
Don’t interfere, don’t offer advice, stay out of it. Pretend you are unaware.
In this way, your child can’t attack you for interference, your grand children aren’t pulled in two directions.
Further, the fact you aren’t talking Mommy/Daddy’s side gives you credit.