Collaborating between iPads

Hello,

I see with iCloud Drive you can share a document or spreadsheet but the other person needs to use a browser on a desktop or laptop. Without putting my iCloud account on all my family devices, I want to collaborate a document with my wife and I on our own iPads. If I cannot do it through iCloud Drive, is there another way we could do it? I figure Dropbox might be a clumsy solution, but I was still hoping for something more built into the iWork suite.

thanks,

Calvin