Maybe something changed but last time I used family sharing would allow only one active game per account at a single time. But you can't go offline and keep playing while slightly risking an abuse detection. You can do the same, or at least could, with 'free weekend' games and play as long as you don't go online.

Another limitation is that this sharing isn't enabled for all games especially competitive online games (the system was widely abused by hackers to avoid bans).