do I play this hand quietly because it's NL .25/50??

[strategem]

Stars NL .25/50 with $50 buy in. I have $77 in lp, dealt K [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/club.gif[/img]. 2 limpers in front of me, I raise to $4, folded to player X (UTG+1) who calls, all fold. Player X ($28 from $50 in about 30 minutes) is really bad - has been calling all the way to the river and losing badly - pockets not even related to the board.

Flop 4 [img]/images/graemlins/club.gif[/img] 2 [img]/images/graemlins/heart.gif[/img] 4 [img]/images/graemlins/spade.gif[/img]..... X checks, I bet $3.50, X calls
Turn 7 [img]/images/graemlins/club.gif[/img]..... X checks, I bet $7, X calls

At this point I figure if he had i.e. A4, he would raise me - is this a mistaken notion?

River is A [img]/images/graemlins/spade.gif[/img]

(4 [img]/images/graemlins/club.gif[/img]2 [img]/images/graemlins/heart.gif[/img]4 [img]/images/graemlins/spade.gif[/img]7 [img]/images/graemlins/club.gif[/img]A [img]/images/graemlins/spade.gif[/img])

X checks, I check and he shows me A2 to win the pot.

My question is twofold - first any comment and criticism of my play would be appreciated. Second ...in situations like this when you are almost certain that your opponent is holding an A and is simply trying to draw out on you, do you bet hard or do you avoid the $7 turn bet because it is so damn likely that the A is coming on the river? Maybe I am weakened by the surreal number of times that my KK has been beaten by a ragged A in the past week or two... but anyway, when you are facing a player you know is not very good, how do you approach this hand? Should I have bet $2 all the way?