A7s in CO

[NomadicRiley]

Just started playing 1/2 6 max at Party after spending quite a bit of time reading the forums here. Had a tricky A7s hand I'd like some feedback on.

BB was brand new to the table, no reads.
MP was loose and slightly aggressive
SB is loose passive

Party Poker 1/2 Hold'em (6 max, 6 handed) converter (http://www.selachian.com/tools/bisonconverter/hhconverter.cgi)

Preflop: Hero is CO with A/images/graemlins/club.gif, 7/images/graemlins/club.gif.
UTG folds, MP calls, Hero calls, Button folds, SB completes, <font color="#CC3333">BB raises</font>, MP calls, Hero calls, SB calls.

Flop: (8 SB) 5/images/graemlins/diamond.gif, 9/images/graemlins/diamond.gif, 7/images/graemlins/heart.gif <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">BB bets</font>, MP calls, Hero calls, SB calls.

Should I be raising this? I was hoping MP would fold so I could raise and isolate BB who I felt could be on overcards

Turn: (6 BB) T/images/graemlins/spade.gif <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">BB bets</font>, MP calls, Hero folds, SB calls.

Is this a weak fold?