While there certainly are other reputed accounts of Jesus’ life, and some of these have the names of apostles attached to them, (for example, Thomas, and James), the evidence seems pretty clear that these Gospels were written long after the death of these apostles. 
 
As for Mark and Luke not being apostles, yet having Gospels, St. Mark was likely the assistant to St. Peter, and so his gospel is largely held to be St. Peter's account. As for Saint Luke, he is very clear to state that he carefully analyzed eyewitness accounts in preparing his Gospel. 
 
Which books ended up in the canon (a word which means "list") of Sacred Scripture was a complex process that developed in the early years of the Church under the guidance of the Holy Spirit. Even through the late Fourth Century there were some disagreements among believers as to which books belonged to the Canon. The Book of Revelation and some of the epistles were disputed. Likewise, some for inclusion in the canon proposed some other edifying writings from the early years, such as the Epistle of Pope St. Clement and the Didache. 
 
The resolution of the final list or canon of Sacred Scripture was largely resolved in a series of Councils in the late fourth century: The Synod of Rome in 382, The Council of Hippo in 393, and the Council of Carthage in 397. These Councils, in consultation with Popes Damasus and Pope Innocent gave us the list of books in the canon of Sacred Scripture that we have today in the Catholic Church. This canon, was largely undisputed until the 16th Century when Martin Luther, removed a number of Old Testament Books and certain other Protestant denominations followed his unfortunate and unauthorized move. 
 
The primary standards used by the Council Fathers and Popes was liturgy and doctrine. Did a particular book have widespread use and acceptance in the liturgy of the Church? Did a particular book comport well with the faith and received doctrine of the Church? These standards, along with some particulars too numerous to mention here, produced the list that we have today of Sacred Scripture. Surely, by faith, we know the Holy Spirit inspired this process as well.

Presumably, you refer to the well‐known musical version of the Our Father by Albert Hay Malotte, which has the soaring doxology at the end: “For thine is the Kingdom and the power and glory for ever and ever. Amen” 
 
Liturgically, this presents two problems. One is the translation of the doxology, which though the difference is minor, is at variance with the approved Catholic translation. 
 
The second problem is that the musical arrangement does not reasonably allow the celebrant to proclaim or sing what is known as the “embolism,” the prayer that begins “Deliver us, Lord, we pray, from every evil, graciously grant peace in our days….” This is because the musical arrangement of the Malotte Our Father is reaching a climax and moves right into the doxology. To stop the song at that moment and have the celebrant recite the embolism is clumsy at best, and does dishonor to the musical setting as well. It is almost like stopping the National Anthem at its musical climax “For the land of the free…!” and inserting a verbal interjection. It just doesn’t work well. 
 
Hence, when the Malott Our Father is proposed for use in the Catholic Mass it is usually sung straight through. But this is improper liturgically. Thus, beautiful though it is, the Malotte Our Father cannot reasonably be used during the Mass. It would seem that it can, however, be used in other liturgical settings with minor adaptions, since in those liturgies the embolism is not required.

A lot of modern skepticism regarding Jesus, and details of the Scripture, center around a rather stubborn refusal to regard the Gospels as an historical source. This a‐priori assumption about the historical reliability of the Scriptures is a kind of skepticism that surrounds almost no other historical documents. 
 
More has been recorded about Jesus than almost any other person in history. There are four rich essays depicting his life, which we call Gospels, and over a dozen epistles. These combine both eyewitness accounts, and credibly collected accounts by others who lived at or very near the time of Jesus. 
 
Some modern scholars like to dismiss these accounts because they are written from the perspective of faith. But all history is written from some perspective. Simply excluding Scripture as an historical source, is neither reasonable, nor does it comport with approaches we use in studying other historical figures and events.