Yes. Your regular meal is there to keep regular food and social occasions in the routine. You can use it for a family breakfast, restaurant lunch or evening meal, depending on the day.
If the event falls at a different meal from your usual regular meal, adjust the meal order so the day still makes sense. For example, keep a family lunch regular and move the planned shake to another meal if that fits your plan.
After an unplanned meal or celebration, continue with the next complete meal. Do not skip food or add exercise to compensate. The aim is a routine you can resume easily.