You could also have them make scrolls and look at Jewish Torah scrolls, as most the the Bible would originally have been written on scrolls. You could, for example, try getting them to write down the rules of your classroom on a scroll.
The word 'bible' comes from the Latin for library. That might be a helpful way in.
You could get them to write a biography of someone -- what things in their life is it important to cover? If they all write biographies of the same person where are the differences, where are the similarities?
Re the collection of the books of the Bible, the majority of the Old Testament was collected during the exile in Babylon. The exiles brought with them various writings from the Temple in Jerusalem which had been destroyed by the Babylonian invaders. During the time they were in exile, they collected, edited, re-wrote and re-ordered these writings into the Torah/Pentateuch (Genesis, Exodus, Deuteronomy, Numbers Leviticus) and the Histories (Joshua, Judges, 1 & 2 Samuel, 1 & 2 Kings, 1 & 2 Chronicles) -- they wrote them into a history of Israel up until the exile, a history which focused on God's relationship with the people of Israel. They also added the Psalms and the Proverbs and some other writings. The post-exilic prophets were added quite a lot later.
The New Testament took quite a long time to be finalised, with Revelation being the last book to be recognised as part of the canon in the 4th century, although the four gospels and Paul's letters were recognised as scripture quite early on.