Provide enough space to accommodate a large table and enough chairs for occupants and guests. Consider how the space might be used for other activities such as homework.

This comfortably sized dining room accommodates a large table and chairs with room to spare. 
(Southside Park Co-housing)

The light filled kitchen/dining area of this Boston townhouse has two separate sitting areas, each of which could be used for other purposes (e.g. homework) when not used for eating. 
(Charlestown Navy Yard)