AK flops 2 pair, how to extract?

[ImsaKidd]

Villain is relatively unknown. Do I absolutely have to bet this turn, or is CR AI ok? Block the river? I was probably calling up to $12 or so on the river.

EDIT: Both players full stacks

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
5 players
Converter

Pre-flop: (5 players) Hero is SB with A[img]/images/graemlins/heart.gif[/img] K[img]/images/graemlins/heart.gif[/img]
UTG calls, CO calls, Button folds, <font color="#cc0000">Hero raises to $2.5</font>, BB folds, UTG calls, CO calls.

Flop: 4[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/spade.gif[/img] ($8, 3 players)
<font color="#cc0000">Hero bets $7.5</font>, UTG calls, CO folds.

Turn: 9[img]/images/graemlins/diamond.gif[/img] ($23, 2 players)
Hero checks, UTG checks.

River: 7[img]/images/graemlins/club.gif[/img] ($23, 2 players)
Hero checks, UTG checks.

Results:
Final pot: $23