I think those kids were desperate for boundaries.
Honestly, the aggression (poking with forks, smashing a potato into the pocket fabric) is so extreme that there had to be a part of them that was screaming, "Stop me! Set boundaries! Make me feel safe. Make me feel like you're in charge, so I don't have to be!"
I'd be calling the parents of those kids and saying, "I'm sorry to say that I'm rescinding your invitation to the party. I simply cannot host your family given how your children acted. Goodbye."
But I also would not have let as much of it go unchecked. I wouldn't have sat there while someone was crawling under the table.