In my house, I would simply remove the child from the table when they starting acting up and say "you must be done eating, go wash up".
If you really want the child to actually manage to eat some food, I would separate the child from the group as soon as they start acting up/playing at the table to their own space. They will not get the attention from their peers that they are looking for, and might actually eat a bit or two. Remind them next eating time what happens if they start to play instead of eat.
This is just an idea - I have not had this problem, so i'm just guessing here
