Subforums as checkboxes in post_tracker?

Hi!

I'd like to show only forum posts in post_tracker (that was easy, added node type = forum post) and let each user specify (with checkboxes) which subforums to show posts from.

As I understand it should be doable with exposed filter, but I couldn't find a way to automatically get a list of subforums, let alone displaying them as checkbox items. Is that possible with Views at all?