What is the ruling on the aḏhān recited by a non-discerning child when there are others more qualified than him, knowing that his family intends thereby to encourage him?

There is no harm in a discerning child giving the Adhan (definition) if the mosque does not have a regular muezzin. Otherwise, it is not permissible without the regular muezzin's permission. It is preferable for an adult or the one with the most melodious voice to give the Adhan. One should not abandon congregational prayer—which is obligatory according to the soundest opinion—on account of this argument.