1 As a prisoner for the Lord, then, I urge you to live a life worthy of the calling you have received. 2 Be completely humble and gentle; be patient, bearing with one another in love. 3 Make every effort to keep the unity of the Spirit through the bond of peace. 4 There is one body and one Spirit, just as you were called to one hope when you were called; 5 one Lord, one faith, one baptism; 6 one God and Father of all, who is over all and through all and in all. (Ephesians 4:1-6, NIV)Yet stating (believing) that, ". . . we are all God's Children" would also assume that God is Father of all. This may be where our disagreements stem from.
"He came to His own, and His own did not receive Him. But as many as received Him, to them He gave the right to become children of God, to those who believe in His name: who were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God." John 1:12,13
All created by God? Yes. All children? No.
God is the source of all life and in this sense He is the Father of all. You are correct that we only become children of God when we believe in Him – He gives us new spiritual life
Who is it that gives mankind that right (to become a child) or the right to receive communion? Is it the Church or the Head of the Church Himself?
Jesus has all authority in Heaven and earth. The question is: Did He bestow this authority? The forum rules do not permit me to discuss this further here. Again, I would love to discuss this with anyone in a one-on-one discussion. Anyone?