Some have argued that the best way to understand the beatitudes as enumerated by Jesus in the Sermon on the Mount is to play a little word game. Try to think of the beatitudes as the "attitudes you sould be".
"Blessed are the peacemakers, for they shall be called the children of God" calls us to change our normal, confrontational attidude we take in life and to move toward a different state of being. We are to become the one who makes peace, not the one who disturbs it. We are called to walk away from gossip and mean spirited behavior. We are called to redirect conflict toward resolution. We are called to be at peace within ourselves so we can share peace with others.
Jesus promises us "my peace I give to you, but it is not the peace of man". Not only as peacemakers are we to work to reduce and resolve conflict and hurt, but we are to bring the peace of Jesus Christ to the world: the peace of knowing that we are not of this world, but strangers here in a strange land. Our home is in another world of eternal peace and understanding and our greatest gift is to import that peace from our homeland to this world.
So, assume the attitude of being at peace in the knowledge of God's kindom and you will be in the attitude of the beatitude and through your peacemaking you will be seen as God's child here on Earth.