Playalong hand: Top Two Pair in Multiway Pot

[aislephive]

Initial opener (CO) is 18/12 TAG. My preflop call is a bit loose but he's raising from late position and I have the button with a solid hand, and can take away the pot postflop without hitting a majority of the time, so I call. Both blinds are solid. SB I have at 17/2 over +100 hands, fwiw.

Ok so it's obviously a good flop, but I do have to be weary as their are a few different straight possibilities out there, but nonetheless my hand is strong. CO bets kinda smallish, I'm not sure if he would bet bigger with an overpair, or KQ, or if his small bet is standard with all of his hands. If I raise, what do I do if somebody comes back over the top? What about my other option, which is flat calling. Is the board to coordinated to just call? Any other thoughts appreciated.

Party Poker No-Limit Hold'em, $1 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

saw flop|<font color="#C00000">saw showdown</font>

<font color="#C00000">CO ($100)</font>
<font color="#C00000">Hero ($98.50)</font>
<font color="#C00000">SB ($113.25)</font>
BB ($107)
UTG ($365.55)
MP ($193.95)

Preflop: Hero is Button with T[img]/images/graemlins/diamond.gif[/img], J[img]/images/graemlins/heart.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">CO raises to $4</font>, Hero calls $4, SB calls $3.50, BB calls $3.

Flop: ($16) T[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, <font color="#CC3333">CO bets $9</font>, Hero ???