Big pot - donk bets, or good value?

[gillabong]

Party 20/40. I don't find myself in big multiway pots often anymore at the Party 15/30 - 30/60 and wasn't quite sure how to play this one. Being a large pot I thought I'd play it aggressive, perhaps too aggressive? Comments welcome.

Reads:

SB is very fishy, roughly 60/20 player and bad on every street.
MP2 is very loose and passive.
The rest seem like decent players, no real reads other than that.

Preflop: Hero is UTG+2 with 5 [img]/images/graemlins/club.gif[/img]6 [img]/images/graemlins/club.gif[/img]
CO posts blind + dead, MP3 posts blind
UTG calls, 1 fold, Hero calls, 1 fold, MP2 calls, MP3 checks, CO checks, Button calls, SB raises, BB calls, 5 more calls, Button 3 bets, everyone calls.

Flop: K [img]/images/graemlins/heart.gif[/img]5 [img]/images/graemlins/diamond.gif[/img]4 [img]/images/graemlins/club.gif[/img] (8 players)
SB checks, BB checks, UTG checks, Hero bets, MP2 calls, MP3 calls, CO calls, 1 fold, SB raises, 2 folds, Hero raises, MP2 calls, MP3 calls, 1 fold, SB calls.

Turn: 8 [img]/images/graemlins/heart.gif[/img] (4 players)
SB checks, Hero bets, 3 calls

River: 6 [img]/images/graemlins/heart.gif[/img] (4 players)
SB checks, Hero bets, 2 folds, SB calls.