55 flop spot

[bender]

I watched my friend play this hand and I was at a loss on what to do on the flop. All options seems slightly appealing to me. Its a 15/30 (6 handed) online game that is juicy where pretty much everybody can be regarded as loose and passive.

Anyway, CO limps, hero raises on the button with 55, both blinds call, and now CO 3 bets, everyone calls. CO is a goofball so the 3-bet doesn't mean much.

Flop: Q 9 3 rainbow. Checked to the 3-bettor who bets, hero...?