Okay, so since we're in need of some ideas, maybe we can start off small with a pirate "job." Raiding a merchant ship with some costly goods they're transporting, maybe? 

If we don't want to have our PCs slaughtering innocents (at least right off the bat), they might find the merchant crew all sick, dying/dead, or even see them being attacked and decide to intervene (before they rob the poor saps blind). 

Then maybe the pirates discover they were carrying some dubious cargo; a cursed item, a rare monster, etc.