Other parent’s kids can sometimes be a problem. However, sometimes other kid’s parents are a greater problem.
Many years ago an acquaintance stopped off at a bar for a mid morning beer and sent his kids, a boy and girl, to play with our girls for the duration. That was okay. Lunch time arrived and Barb set places for his kids too.
They didn’t want to wash. They protested loudly, but Barb informed them if they wanted to eat they would first wash. They washed. But there was a price to pay.
When he dropped by to pick them up they set up a howl about being made to wash and he lit into Barb.