Negative criticism and unpleasant topics are not appropriate dinner fare. Involve the children in the dinner conversation. Their participation will help them feel valued and also expose them to the art of conversation. Learning how to take turns speaking and listening are important skills for all areas of life. Specific questions to children are more likely to trigger conversation than general questions.
Laughter is the best dinnertime music.
Family dinners don't always have to be evening events. They can be weekday or weekend breakfasts or lunches. The most important thing is communicating the importance and desirability of family meals. Change the family dinner location. A picnic or meal in another room keeps the mealtime experience enjoyable.