Business directory with multiple locations using custom post types

I have been searching for hours on this and can’t quite find the answer to my question.

I am building a custom business directory for my client using custom post types. Each business (well, in our case they are restaurants) has multiple locations – some are nationwide and have thousands.

I cannot figure out what would be the best way to go about this. Ideally I could make a “Locations” post type that was a child of “Restaurant” post types, but I don’t think that’s possible at this time.

It’s important that there are actual locations with “Address”, “City”, “State” etc being separate strings of information all applied to one entry.

Is there a way to add infinite meta boxes like this? Does anyone have any experience or suggestions how I could put this together?