Beijing opens up all of Asia for them, but assuming they're staying within China and the next leg is tomorrow they could be on one of these. China has so many airlines that between major cities, flights are approx. once an hour, there are tons daily. My money is on Xian, due to the Terra Cotta Warriors, but there are amazing landmarks in all of these destinations that would make great TV, and flying back to Canada from all of them is not hard, the airlines work with Air Canada.
Xian -
China Southern 3173 PEKXIY 0655 0905
China Airlines 1231 PEKXIY 0735 0945
China Eastern 2102 PEKXIY 0755 1000
Shanghai -
China Eastern 5183 PEKPVG 0740 0950
China Airlines 1835 PEKPVG 0800 1015
China Eastern 271 PEKPVG 1305 1520
Guilin -
Grand China 7215 PEKKWL 0745 1100
China Southern 3282 PEKKWL 1220 1530
China Airlines 1471 PEKKWL 1235 1545
China Airlines 1225 PEKKWL 1520 2050