100NL extracting with a rivred flush

[bsheck]

Table is overall loose/passive, but they are capable of folding when the scare card comes. UTG in this hand is somewhat decent. CO I've seen call a few hands down on the flop & turn only to fold the river. I have around $110 to start the hand, both villains cover.

$.50/$1 6-max Merge Network.

UTG limps, MP folds, CO limps, BTN limps, I complete K[img]/images/graemlins/heart.gif[/img]7[img]/images/graemlins/heart.gif[/img] in the SB, BB checks.

Flop ($5, 5 players). [Q[img]/images/graemlins/heart.gif[/img],3[img]/images/graemlins/heart.gif[/img],4[img]/images/graemlins/club.gif[/img]]
I check, BB checks, UTG bets $4, CO calls, BTN folds, I call, BB folds.

Turn ($17, 3 players). [Q[img]/images/graemlins/heart.gif[/img],3[img]/images/graemlins/heart.gif[/img],4[img]/images/graemlins/club.gif[/img]] [9[img]/images/graemlins/diamond.gif[/img]]
I check, UTG bets $7, CO calls, I call.

River ($38, 3 players). [Q[img]/images/graemlins/heart.gif[/img],3[img]/images/graemlins/heart.gif[/img],4[img]/images/graemlins/club.gif[/img]] [9[img]/images/graemlins/diamond.gif[/img]] [6[img]/images/graemlins/heart.gif[/img]]
I'm first to act and I...?

I believe UTG is folding if I bet out here, likely CO as well unless he has a flush with me (or 2pr or a str8). Should I just sell my hand cheap here (even $15?) and take what I can get? What about checking? Also, did I play it okay on the other streets?