KQ flopping K with A on board

[Lunkan]

Party Poker 1/2 Hold'em (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is UTG with Q[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Hero raises</font>, <font color="#666666">4 folds</font>, MP3 calls, CO calls, Button calls, <font color="#666666">1 fold</font>, BB calls.

Flop: (10.50 SB) K[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, MP3 calls, CO calls, Button calls, BB folds.

Turn: (7.25 BB) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">Hero bets</font>, MP3 folds, CO calls, Button calls.

River: (10.25 BB) 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, CO checks, Button checks.

Final Pot: 10.25 BB

I guess betting the flop into 5 players with second pair and a backdoor flush is wrong?

On turn I planned to fold to a raise and on the river to call if it was one bet back to me.