Party 2/4, AQo with heavy resistance

[PantherZ]

Kind of a weird hand to start with. There are two extra blind posters (UTG+2 and MP3). The small blind is a fish calling station. The BB seems slightly loose preflop and aggressive postflop.

Party Poker 2/4 Hold'em (10 handed) converter

Preflop: PantherZ is MP1 with A[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/diamond.gif[/img]. UTG+2 posts a blind of $2. MP3 posts a blind of $2.
UTG folds, UTG+1 folds, UTG+2 (poster) checks, <font color="#CC3333">PantherZ raises</font>, MP2 folds, MP3 (poster) calls, CO folds, Button folds, SB folds, BB calls, UTG+2 calls.

Flop: (8.50 SB) 5[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, UTG+2 checks, <font color="#CC3333">PantherZ bets</font>, MP3 calls, BB folds, <font color="#CC3333">UTG+2 raises</font>

All of a sudden, AQo isn't looking so invincible here. To be checkraised heads-up is one thing, but how about this situation where a player checkraises two opponents?

What's the best line here? 3-bet (and what if he 4-bets?) or just call down.