Slowplay?
 

PokerStars 0.50/1.00 Hold'em (6 handed) converter

Preflop: Hero is Button with K[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 fold</font>, MP calls, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises</font>, SB calls, <font color="#666666">1 fold</font>, MP calls.

Flop: (7 SB) 5[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, MP checks, Hero checks.

Turn: (3.50 BB) 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets</font>, MP folds, <font color="#CC3333">Hero raises</font>, SB calls.

River: (7.50 BB) 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, SB calls.

Final Pot: 9.50 BB

Villain seems pretty straight forward pre-flop and post-flop

Also, against a brand new opponent how would this be?

Re: Slowplay?
 

Looks fine to me, since it is only 3 handed. With a few more players in the pot I'd bet this out and push any draws people might be on out of the hand. Against an unknown I'd probably play it the same. Nice hand.

Re: Slowplay?
 

Without reading your post, I'm 90% sure the answer is no.

Edit: Upon reading your post, my answer is still no. You lucked out on the turn that MP2 bet for you, allowing you to raise. Had he not obliged you, you would have felt pretty stupid about this hand. There's a potential straight draw out there, as well. No sense in giving a gutshot a free card to outdraw you.

I don't think I've slowplayed anything less than a flopped nut flush, and I don't think I've ever checked behind on the button with a made monster ever, no matter how big my hand was. People like to call bets, especially on the flop. Let them.