AK flops top pair on a 3 flush board - advice needed

[remen]

This hand is from the Pokerstars afternoon 5.50 + rebuy tournament. The rebuy period is over and I had my tabled moved about 30 minutes ago. My table image was very tight, as I was playing very tight due to the table being full of call stations and LAGs. This is the first hand I have played in about 10 minutes. Both villains in this hand were extremely loose preflop seing over half of the flops for any amount. The CO was pretty much a call station post flop, he rarely raised. The button was pretty aggressive postflop. I am fairly sure the CO was on a flush draw. The button could have any king, KQ, a made flush, a flush draw, or a total bluff. Would you have played it any differently up to the flop and how would you react to the buttons flop raise?

The hand:
PokerStars No-Limit Hold'em Tourney, Big Blind is t400 (9 handed) converter

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

CO (t45549)
Button (t34161)
SB (t11045)
BB (t47707)
Hero (t22531)
UTG+1 (t16265)
MP1 (t14685)
MP2 (t9985)
MP3 (t18265)

Preflop: Hero is UTG with K[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Hero raises to t1200</font>, <font color="#666666">4 folds</font>, CO calls t1200, Button calls t1200, <font color="#666666">2 folds</font>.

Flop: (t3800) K[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/spade.gif[/img], 2[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets t4000</font>, CO calls t4000, <font color="#CC3333">Button raises to t8400</font>, Hero ?.