Are they able to read Roman characters? If so, they should be able to look at flight displays and then at the signs to the gates. I've been to more airports than I can count where I haven't spoken the language. Fortunately, every airport I've ever been in has used Roman characters in addition to whatever their alphabet is. If they don't read Roman characters, can you provide them with translations of the city to which they are traveling in their own language and English?