Is not raising top set wrong in this spot?

[KSOT]

Party Poker 2/4 Hold'em (9 handed) converter

Preflop: Hero is UTG+1 with 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/club.gif[/img].
UTG calls, Hero calls, <font color="#666666">1 fold</font>, MP2 calls, <font color="#666666">3 folds</font>, SB completes, <font color="#666666">1 fold</font>.

Flop: (5 SB) 9[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, UTG goes all-in for $2, Hero calls, MP2 calls, SB calls.

Figured it might be worth the risk to keep MP2 and SB around if they wanted to come. I 'woke up' on the turn of course...