Crew aren't Bystanders. They're Allies. There's a difference.
One of the differences is the player gets to pick their motivation from the list on page 119, unless the move specifies it. Even for a Crew, it's one motivation that tends to give everybody the same purpose, for all that Fat Larry likes to hang back and keep watch and Li'l E can't get enough treasure.
Another one of the differences is that your player bought them with a character creation choice or an advance, and as such they're something cool and important about the character and shouldn't casually be brushed aside, the way you'd just drop a Bystander into a screaming red pit in the earth if you had to.
Crew, By the Numbers
Unlike, say, your Chopper's Gang from Apocalypse World, Crew don't have a lot going on with them mechanics-wise. This is pretty much by design, according to the author over here.
If a PC is working with them, Crew expand the narrative scope of what they can do, not boost the numbers on their rolls. If a combat situation comes up and the Crew have harm (as established) to deal, just stack it right on top of whatever the Crooked's swinging with already. It's not gonna be a big deal, given how you can point your PCs at some real chufty boys. And remember: when you inflict Harm on a chufty boy, the chufty boy inflicts Harm also into you. So somebody's got to take that bullet.
You don't necessarily care about any of that, I know, but I figured I'd get it out of the way as the short bit before we get to the real main feature:
Crew, By the Book
By which I mean their role in the story. And, it doesn't sound like you actually have the problem you think you have? The PCs are the central hub of the story and when it gets down to the crisis point it's all of them together, and anything out in their periphery is only in there with them if it's really going to matter.
So don't beat yourself up over perceived shortcomings; if your Crooked is satisfied with what they're getting out of their Crew in the story, then you're doing fine. (And, I mean, you should be taking your playgroup's temperature on the reg as regards all that, at the very minimum asking them, at session end, to name something they liked about the session and something they'd like to see next time.)
But okay, maybe your Crooked is dissatisfied, and you shouldn't just ignore your own discomfort for the sake of the group; you're here to have fun, too, after all. Here's what to do.
- Establish a baseline. What are the Crew doing on a usual day? Insurance fraud for some extra cash? Taking the temperature of the streets? Keeping an eye on some arc threat that's on a slow boil? Your Crooked knows, so ask, and don't accept any "remain motionless in this locked room"-style answers; they're people, and they need fresh air and sunlight, or at least smog and moonlight. Once you know what the Crew tend to do:
- Offer an opportunity. Not too often, but stick a post-it on your DM screen and tear it down when one of them volunteers to do something that doesn't seem to be all that dangerous. Even if the PCs are meeting in what they consider to be a secure location - this is the Crooked's Crew, after all. Or you could have one of them tail a PC if they're splitting up and offer a less risky but more legally dubious way of getting things done.
- If the PCs delegate, tell them the consequences. The Crew are in your hands, Keeper. How they do their job and what move you present to the PCs is totally up to you. Maybe it is small potatoes and they take care of things just fine. Maybe they're in over their heads and come back with something the PCs should really investigate. Maybe they're in way over their heads and the PCs have something more than investigating to do.
Don't worry about them showing up in every climactic battle, especially if nobody's taken steps to gear them up for it. They work a lot better informing the plot that gets the PCs there. I mean, not every climactic battle is going to romp on through the Expert's Haven, either, but it's still impactful in most sessions, isn't it?
(And of course, they don't have to make entirely positive impacts either. The Crooked rolls a 4 trying to Act Under Pressure and bring out the ruby-eyed skull pendant that will seal the screaming red pit in the earth? Oh yeah, they asked Li'l E to look after it. ...oh yeah, they asked Li'l E to look after it.)