Hi there @jai713, thanks for posting in the Community! : )
Spotify Premium for Family, allows the owner to add up to 6 people in the Family Account. Your son will be able to play his music, with or without wifi, without any problem.
If you mean, if he will be able to Listen Offline, yes, after he download his favorite playlists! (download music, doesn`t use MB`s of your celluar data)
Hey there you,
Yeah, you! 😁
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