Wait, they let you set up a board game in the office? My old boss would have lost it if we even had cards out on a desk. How did you get everyone to agree to play during lunch?
Seriously, we started with a game that only takes fifteen minutes, like Skull. Left it set up in the break room so people could just wander over and play a quick hand. After a couple weeks, the boss just sort of accepted it, probably thought it was team building or something.