Teaching the good manners to the children is very important. It will affect their future life and build their personality. Without the good manners the children will have less self-control, over-confident, reckless, no respect with other people and many relationship problems in their life.
Children are different with adult, especially at their early childhood. Normally their logic and reasons is still undeveloped, very impulsive and tend to loose control without proper supervision from the adult. That is why it is not easy just to tell them what to do and what is not to do. They need to know why and realize why some behavior is not acceptable.
Teaching the good manners
As parent we tend to have huge tolerant when our children making ruckus, because that is a normal behavior for young children. This behavior may seem okay if they are in their private environment. Unfortunately when they are on the public environment, this behavior cannot be accepted. Therefore as parent you must step in and control your children.
The best way to deal this situation is by separate them or taking them from public to the close or private environment. Wait until they calm down then tell them calmly that their behavior is unacceptable because it makes other people become inconvenient and disturb other people in many ways or even hurt other people. Therefore they will know and learn in the proper way how to act in different condition, environment and situation.
When the children become older and their logic is develop and trained, then you can teach them verbally about the proper manners.
For children better future
When the children do not learn the good manners, they will assume that is alright to disregard and violate other people right, peace and space. They will grow up as irresponsible person that do not care about other people. People will pull a distance on them accept other irresponsible person too. I doubt any parent will want this kind of future for their children.