If you happen to be teaching at the intermediate level, Coup is a really effective game to use. The main benefit is that the language to be used during the game is fairly limited, so children can learn it quickly, and use it effectively. And it’s a great game: the game mechanic of bluffing about what cards you’re holding is absorbing, so kids will genuinely enjoy the process.
I teach it like this: first I play a round in which everyone’s cards are face-up on the table, just to teach the mechanics. The players will need to learn the new vocabulary like assassin, duke, ambassador, tax, etc. If you need, you can write a vocab cribsheet with the equivalent in the children’s native language. I tend to have really engaged groups of kids, so I find I can do it orally. During this round, there’s no bluffing, obviously, but everyone learns the basic moves to be made in a round.
Then in the second round, I tell everyone to pick up their cards and keep them hidden, and introduce the idea of lying (I teach “lie” rather than bluff, just as a slightly more common word.) I do some obvious lies/bluffs myself so that they have a chance to practice challenging, and they get to enjoy killing the teacher. Once that’s done, we can start playing for real.
As with any game-based lesson, the challenges involve minimising talk in the native language, getting kids to pay attention to the English being used, and to remember to use language correctly, rather than getting too carried away by the excitement of the game. But I think the benefits in terms of engagement and using the language communicatively are enormous. Also not to be sneezed at: making children happy is surely one of the best things a person can do in the world. I use games quite regularly, and Coup is definitely one of my most successful picks.