When the grandkids are around, the dog feels a need to supervise their activities. There's just no telling what those grandkids will get into, especially the younger ones. They're always poking and prodding in places they shouldn't, and without a dog's supervison, they're likely to get into trouble.
It doesn't matter which kid is around, the dog is there somewhere keeping them out of trouble.
Ya gotta keep an eye on them!