NL50 KK Ahi monotone flop vs shorty

[checktheriver]

PokerStars No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

MP ($6.70)
CO ($12.75)
Button ($25.55)
SB ($31.70)
Hero ($39.10)
UTG ($14.05)

Preflop: Hero is BB with K[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">CO raises to $1</font>, <font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises to $3.5</font>, CO calls $2.50.

Flop: ($7.10) 5[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>

Villain just sat down so no reads. What do you do here ? check/fold, bet/call or crai hoping he just has a high heart enough (given that the Ah is out this seems to be a small part of his range)?