Yeah don't just use a sm57, if you do use it grab a DI signal as well as you'll be lacking in the low end with just a 57.
Electro voice re-20 is the best I've heard a bass amp recorded, else Heil PR-40 so see if he's got one of them knocking around (unlikely if he's opting for a 57)
Also remember it's your bass sound not the producers, I say this because it sounds you're recording your band and not sessioning. He might know best, but then again he might just be a guy who bought some software and is now an expert, I leave it up to you to make that assessment of him.