So, I’ve decided to stick to simple categories instead of marking the diary posts as part of an article. So gaming diary posts are in that category and movie diary posts in their own. I’ve hacked the category page a little so that the post titles have the dates next to them (and they naturally show in reverse date order, newest first anyway).
That avoids any complexity, I can just name the posts after the game or film and let WordPress sort out the rest, but people can still see them in the right order as it were. The only other issue is that I’ll probably write any gaming diary posts a few days after the fact, so now I have to work out if I’ll post-date them to match when I played or not worry about it! I know, I know, I should just go with the flow.