Is the father's prayer with his 8-year-old son considered a congregational prayer, and is he required to raise his voice with the Takbir in this case?

Scholars differ regarding whether one attains the virtue of congregational prayer when praying with a boy. Some affirm it, such as Imam An-Nawawi, while others do not. The latter view holds that whoever prays with a boy is recommended to repeat the prayer with a congregation. This is the madhhab of the Malikis and one of the two narrations from Imam Ahmad. According to this opinion, whoever prays with a boy in congregation is as if he prayed alone, and it is recommended for him to repeat the prayer with a congregation.

There is no disagreement that a man's prayer in the mosque is better than his prayer in his home. As for raising the voice with the takbir for the imam, it is among the recommended acts.