[BluffTHIS!]

I'm as big a fan as anyone of betting when checked to, but this is an unraised pot and you have someone yet to act behind you, and with a hand that has the potential to both make a monster or get you in trouble. So with no real equity to protect in a multiway pot, checking and calling a reasonable bet is the line that lets you possibly make a hand to break someone, while not risking getting run off that opportunity either. All this assumes you don't think this is a hand worth goint to the felt with on the flop in a multiway unraised pot, which I don't.