25NL: turn 3rd nut flush in limped pot, what to do?

[sweetwater]

MP1 is 40/4/.3 over 45 hands, no stats on MP2

once MP2 flat calls I'm kind of lost.. is calling then c/c any river okay here?

Poker Stars, $0.10/$0.25 NL Hold'em Cash Game, 9 Players
LeggoPoker Hand History Converter

MP2: $14.60
CO: $19.60
BTN: $24.85
Hero (SB): $35.55
BB: $9.90
UTG: $25.05
UTG+1: $29.35
UTG+2: $5
MP1: $14.90

UTG+2 posts $0.25
MP2 posts $0.25
Pre-Flop: J[img]/images/graemlins/spade.gif[/img] Q[img]/images/graemlins/spade.gif[/img] dealt to Hero (SB)
2 folds, UTG+2 checks, MP1 calls $0.25, MP2 checks, 2 folds, Hero calls $0.15, BB checks

Flop: ($1.25) 4[img]/images/graemlins/spade.gif[/img] 8[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/spade.gif[/img] (5 Players)
Hero checks, BB checks, UTG+2 checks, MP1 checks, MP2 checks

Turn: ($1.25) T[img]/images/graemlins/spade.gif[/img] (5 Players)
<font color="red">Hero bets $0.50</font>, 2 folds, <font color="red">MP1 raises to $3</font>, MP2 calls $3