I got this idea from one of the Spanish SSiS coffee mornings.
I brought in the cards from Cluedo and we had to explain to the others what was on the card so others could guess. (And where how I learnt the fantastic word Pavo real!).
Expanding on this, board games are great opportunity to speak with others in a situation that has a limited vocabulary. You're basically saying more or less the same stuff over and over again with variations, a bit like the SSiW lessons.
What about a printable page of key vocab to have to hand when people are playing.
eg. the Welsh for: Check, your turn, cheater, The billiard room, The gas works, etc.
Make different ones for different games.