Okay, so I'm BB with pocket 6s. I get 4 callers, should I raise and try to force people limping with crap hands to fold, or should I check to possibly get a set for free?

EDIT: This was a hand I played early on in a NLHE freeroll on Pokerstars (one of the ones that qualifies you for a prize money tournament), so a lot of fish were still there, two of the callers seemed to be playing pretty well, taking down many pots and whenever it went to a showdown they had a hand.