Live 6/12: Straight Draw on the button

[jesse8888]

In the hand in question, I actually folded pf. However, let's play this hand assuming I'd made the call.

Hero holds 35o on the button. 3 loose passives limp in and hero limps. SB completes, BB checks, and we're 6 handed to the flop.

46Qr

SB bets out and two players call. The better is straightforward....he likely holds a Q. The loose passives could have a wide range, but likely have some sort of viable draw (one pair, a back door flush with an over....they probably aren't going to show up with 7To at least).

What's hero's action? My initial thought was "Hey, this is a great time for the free card play". Is that what I should be thinking? Or is there more to it? There is no need to knock anyone out; if I hit, I will win, and if I don't, I will not, almost regardless of how many opponents remain.

More to follow after a few responses.