Explain the expectations, and motivate them to rise to the challenge. Match the meal to your children's tastes. Decide whether to take all of your children at once. If parents have two children, they can play one on one. With three or more, it's more like zone defense.
Children often do well at a buffet.
They see the actual food, serve themselves quickly and make choices. Some family-run ethnic restaurants are more tolerant of children. Their own children may have been hanging around the kitchen for years. If the restaurant does not own a high chair, they are telling you something. Try not to take them out to eat when they are tired.