NL100 - 3-Bet shove with low overpair on this flop?

[SuchaDonk]

NL100. Villain is about 21/18/4 over about 100 hands.

I realize that I'm probably either beat or against a semi-bluff. Is villain semi-bluffing here frequently enough to make a shove correct? Or is he too likely to have a set or JJ,QQ?

Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Button ($98.50)
SB ($108.90)
BB ($201.70)
Hero ($149.30)
MP ($320.20)
CO ($99.50)

Preflop: Hero is UTG with T[img]/images/graemlins/heart.gif[/img], T[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises to $3</font>, MP calls $3, <font color="#666666">1 fold</font>, Button calls $3, <font color="#666666">2 folds</font>.

Flop: ($10.50) 9[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $8</font>, MP folds, <font color="#CC3333">Button raises to $32</font>