A crew is made up of one Heritor, one Warden, and up to eight crewmen of various stripes. Basic crewmen share a statline, but have four different weapon loadouts to choose from, while specialist crewmen have fixed loadouts and generally represent tougher or more specialized options. You can have a maximum of 4 specialists in your crew.
In fluff terms, like Frostgrave, it's pretty much anything goes. If you want your crew to be a pirate captain leading his mob, go for it. The scion of a noble house with his bodyguard? Yup. A scholar accompanied by hired mercenaries? Cool. My own crew will be themed around a crimelord (who has risen to power thanks to his Heritor abilities), with the specialist crew representing his henchmen, enforcers, and whatnot, and the basic crewmen being the actual crew of the ship he commissioned to transport him to the Ghost Archipelago.
All of those Zanzibaris (except for the shotgunner) would work fine! You might be a little light in terms of ranged attacks, but I'm sure Gripping Beast/Artizan/Footsore Arab/Saracen/Moorish archers would fit in pretty well, and the tribal archers from the Darkest Africa range would work well too - perhaps they represent one of the tribes native to the Lost Isles (the descendants of the survivors of a previous expedition, maybe?) or levy troops from the Zanzibari Heritor's home territories?