Enquiry on whether to get G or L visa

My father, sister, and I will be transiting through China in late December (coming from Japan and going to Bangkok through Beijing). My sister and I are Australian citizens, and my father is a Thai citizen.

From what I understand my sister and I can leave the airport (Free transit) for up to 72 hours, but my father (Thai citizen) will need a visa. We will only stay for 1-2 days. May I check if it would be appropriate for him to get a G,or should we apply for an L?