fresh AA hand, weak river play?

[ccwhoelse?]

table is pretty loose and passive

Party Poker 0.5/1 Hold'em (9 handed) converter

Preflop: Hero is MP2 with A[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/spade.gif[/img].
UTG folds, UTG+1 calls, MP1 folds, <font color="CC3333">Hero raises</font>, MP3 folds, CO calls, Button calls, SB folds, BB calls, UTG+1 calls.

Flop: (10.50 SB) 3[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/spade.gif[/img] <font color="blue">(5 players)</font>
BB checks, UTG+1 checks, <font color="CC3333">Hero bets</font>, CO calls, Button calls, BB folds, UTG+1 calls.

Turn: (7.25 BB) 5[img]/images/graemlins/diamond.gif[/img] <font color="blue">(4 players)</font>
UTG+1 checks, <font color="CC3333">Hero bets</font>, CO folds, <font color="CC3333">Button raises</font>, UTG+1 calls, Hero calls.

River: (13.25 BB) K[img]/images/graemlins/club.gif[/img] <font color="blue">(3 players)</font>
UTG+1 checks, Hero checks, <font color="CC3333">Button bets</font>, UTG+1 folds, Hero calls.

Final Pot: 15.25 BB
<font color="green">Main Pot: 15.25 BB, between Button and Hero.</font>

i thought my river check-call was pretty weak given that the board paired. thoughts?