From this verse, it seems that baptizing little children must have developed fairly recently in Nephite religion; and Moroni, perplexed by the practice, consulted his father. Probably Mormon had an opinion on the subject before taking it to Yahweh in prayer, but he was following the proper mode for resolving doctrinal difficulties. Human reason is a powerful tool of agency, but it was precisely how the disputations had arisen in the first place.
The fact that Moroni had to write to his father, telling him of his call to the ministry and describing this doctrinal problem, reveals that Mormon is so far away that Moroni must send a messenger with the letter—also that he did not expect to see his father soon enough that he could wait and consult him in person. It also tells us that Mormon did not know of Moroni’s call to the ministry and did not ordain him to that office. Presumably, therefore, a functioning quorum of twelve was still leading the Nephite church, even though they are not all in the same location. In this terrible time of war, perhaps Moroni had been called to replace an apostle who had perished in battle.
Less clear is why Moroni asked Mormon about the baptism of little children rather than asking the apostle(s) who had ordained him. Perhaps Mormon had a senior position, and a point of protocol was involved. Perhaps Moroni was aware of the issue to a different degree than his fellow apostles and felt more comfortable taking the question to his father. Perhaps there was a difference of opinion among the elders.