$100 3 left, marginal spot with AT

[smittyuiop]

Long time reader first time poster. This spot had me pretty confused.

Full Tilt Poker No-Limit Hold'em Tourney, Big Blind is t120 (3 handed) Hand History converter Courtesy of PokerZion.com

Hero (t2950)
Button (t5090)
SB (t5460)

Preflop: Hero is BB with A[img]/images/graemlins/diamond.gif[/img], T[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Button raises to t420</font>, SB calls t360, Hero...??

Button is good TAG player, whenever he plays a hand he plays it really strong, usually clicking 'POT' then 'BET' at his action. SB is aggressive but a little loose and ran good to get to last 3. Shove picks up 900 or so but could likely be dominated. A stop n go raise to 1300 might look scary but probably commits me. Anyway I called...

Hero calls t300.

Flop: (t1260) Q[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero checks, <font color="#CC3333">Button bets t1260</font>, SB folds, Hero ...?

He thinks for just a little bit and pots it, which is half my stack. Stick it in, or does he have to have a bigger hand to bet that strong into two people who called his pf raise and are very likely to have hit that flop?