Ax Suited - Mistakes?

Party Poker $0.15/$0.30 (9 handed) converter didn't work, had to hand jam bets.

Preflop: Hero is UTG with 3[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/spade.gif[/img]. Villain is SB and has seen 57% after 19 hands with three previous preflop raises.
<font color="#666666">1 fold</font>.Villain raises, BB Folds, Hero and Remaining 5 Players Call.

Flop: 3[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(7 players)</font>
Villain checks, Hero Bets, 3 Players and Villain Limp. 2 Folds.

Turn: A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(5 players)</font>
Villain checks, Hero Bets, UTG+1 Limps, MP1 Folds, CO Limps, Villain Raises, Hero 3Bets, UTG+1 Folds, CO calls, Villian Caps, Hero and CO call.

River: 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
Villain Bets, Hero Raises, CO Folds, Villain 3Bets, Hero Caps, Villain Calls.

Final Pot: 31BB


Thoughts: Preflop, I played this out of position, but with the late raise and 7 players already VP$IP I have no problems calling a raise here. Flop, no reason not to bet a set with an ace kicker. Turn and river, I hit the boat, but is capping twice wrong here? I see a couple of worst case scenarios (AA/A9/99), but I assume I am crushing this and bet accordingly.

Edit: Wan't looking as I typed my thoughts: AA/99/88 would be the ones to watch. (Thanks to posters for pointing this out)

Results in white below:
<font color="#FFFFFF"> MHIG, Villain Shows Flush with a 10 and a 4 of Clubs. This is a preflop raise, I'm wondering if it's ok to assume your opponent is an idiot until proven otherwise. </font>