Paul,
We'll have to do some testing with this. The K2 Open Graph plugin should work on the category you select and any of it's sub-categories. It was designed so that you could set a top-level object and then even define a new object for a specific child category. That way, you have a lot of flexibility for a 'default' type of object but can still set objects for a specific subset of categories.
Can you test some more and check to make sure it's not working how you expect? Specifically, there may be an issue with Open Graph Actions not working on the sub-categories, but the tags *should* be set correctly. I hope that makes sense.
We will look into this further, but it may take a day or so to get a response to you.. any info you can provide from the above would definitely speed things along.
Thanks,
Alex
OpenGraph Object - K2 sub-categories
