As parents one of the most important things we can give our children is stability. Often our children will act out when things are going differently then they expected. If your children have been struggling with Sacrament meetings or family home evenings establishing a routine and order to help your children to know what to expect may help them to change their behavior.
You can set up a Sunday morning routine that will set it apart from other days of the week. This way your children are preparing for Sacrament meeting from the beginning. Sunday may be the day that you eat a big breakfast together. Or if you have meetings later in the day you may spend family time together writing in your journals. Adding a Sunday only activity to the mornings can help your children change their thinking about the day.
It is also important to try to avoid the rush that comes with getting out the door Sunday morning. This can end with hurt feelings, and a general grumpiness. Grumpy kids do not like to sit still and quietly. If you plan as well as you can and start early enough you can avoid the rush and help your family arrive at church peacefully. Before you leave for church remind your children what behavior your expect of them.
Family home evenings and scripture study can be handled in a similar way. You may want to have a set place to meet or some signal for your children. One family I know calls the family together for family home evening by singing the same song every time. This helps your children to switch into the correct behavior for the activities.
As parents we need to work on expressing to our children the behaviors that are expected of them. We also need to give them time to transition into the activities. By addressing the way your family handles the transitions you may be able to help your family behave better overall.