Is is possible to export only a subset of posts?

I have a site which has approx 100 categories .. I want to export the posts from only 17 (a parent, plus 16 child) categories. My choices in the default export are either 1 category or all of them..

The only thing that comes to mind is to create an empty blog, import ALL to this blog, then delete everything I don’t want and only then create the export file that my client has requested.

Is there a shorter path??