As for me, an offline storage is a nice suggestion. I think, an SQLite storage would provide an organized, lightweight and simple way to do this. While playing, the game continuously saves log data, but, when the game discovers an opportunity to synchronize, it is simply performed in background.
When synchronizing, the game makes an HTTP request to specially designed web service of the blog. The service gets the data, process it, authorizes the uploader user, and finally makes a post to the blog.
Btw., I’ve made a mistake about master->master, it is more of master->slave relation type.