I had first hand experience with these guys.
My parents came to US in this airline.
Tickets were really cheap and it costed $800 round trip with insurance for each.

Pros:
-Cheap
-On time if flights are confirmed
- Two 50 lbs luggage for each passenger.

Cons:
-In China, no one speaks English and my dad had to use translation app to communicate.
-Both of my parents were vegetarian and I specially paid $60 extra for their food which they didn't get while coming and going back. Funny thing is they gave food with some chicken and when my parents said they were vegetarian, the hostess opened the box and removed the Chicken with the sauce still in it.
-They landed in LAX and they were asked way too many questions and baggage was scanned twice. (Maybe due to Chinese Airlines?)
-Customer service is a joke as no one picks up here in the US. It always goes to voice mail
and no one calls back.
- When my parents were going back, although I booked the return flight months ago, they said seat was not confirmed from Shanghai to Kunming. But other flights are confirmed. When I asked if they could provide hotel if that flight is not confirmed, they said they have to wait in lounge and it can take 12 to 48 hrs. And for 3 weeks, the flight got rescheduled by me to ensure all flights were confirmed. It was a blessing in disguise for me too as my parents wanted to spend some more time with me. So, in summary if your relatives are planning to leave in nick of the time before their visa expires or other important task back home then this airlines is a no no.

Let me know if you have more questions.