The Afikomen is the last piece of matza to be eaten at the Seder. It is part of the middle matza that has been hidden at the beginning of the Seder. The Afikomen must be eaten before the Seder can be completed. 

Traditionally, the children try to find it and are then in a good position to bargain with the leader to get it back. This symbolizes the right of children to be heard and to be involved in family decisions and of their importance in our future.

Although everyone will eat a last piece of matzah, the search for the afikomen will be different because of the number of children present.

Song: Hiney Mah Tov

Hiney mah tov
She-vet a-khim-gam-ya-khad

Behold how good and how pleasing for brothers (people) to sit together in unity.

haggadah Section: Tzafun
Source: The Jewish Secular Community Passover Hagada