My first stop would be checking if the journal has any particular authorship policies. If it does, follow them - if its not the way your field does it, welcome to the perils of interdisciplinary research.
From there, in my mind, it splits into two questions:
- Is it a field-specific paper that happens to be going in an interdisciplinary journal. For example, are all the authors from Alphabetical Author List Field? Then put it in that field's ordering.
- Is it genuinely interdisciplinary (multiple fields with different traditions)? I'd probably default to the non-alphabetical ordering scheme, as among people I work with its the more common ordering scheme, and those who come from other fields that don't do that are generally pretty understanding. Or, if the authorship list is small enough, see if there's a clever ordering of author names that gets everyone what they need (it happens).