You might consider getting them some kind of "cheat sheet" where you spell out English words they might encounter and the Mandarin equivalent. I'm thinking of words like "Shuttle", "Toilets", "Departure Gates", etc.

Another good idea would be to make up a card with something like "We do not speak English. We speak Mandarin. We need to go to the following flight...." They could simply show that card to a uniformed airline or airport employee and hope the person points them in the right direction.