Anatomy of a preflop decision A9o

[Bona]

I'm in the hijack seat with an unknown poster behind me.
CO is the unkown poster.
Button is playing reasonably tightly and semi aggressive 20/6.5/1.5 45 hands
SB is loose passive 40/0/.67 32 hands
BB is semi loose but pretty aggressive at 25/10/2

I am dealt A [img]/images/graemlins/club.gif[/img]9 [img]/images/graemlins/spade.gif[/img]
MP1 limps he is loose passive 56/2/1 I believe is very likely to take his hand to at least the river. Often showdown.

I see my hand as weak/marginal multiway but likely better than any one of the villains. 3 of the 4 behind me are posters and two are loose players so I expect I can't isolate the limper and probably would have 2 more callers if I raise and 3 if I call.

I was very tempted to get in here, probably with a raise if I did, but I folded the hand. Is that a correct decision?