I don't use the same platform but you might get some ideas from our class blog. We do have RSS news feeds coming in--it's hard to find feed that is OK for kids. N.
I didn't make my point, I tend to expect my reader to read my mind. Let me start over---one of the options for "what can I write about?" is allowing students access appropriate news feeds coming in to your site by RSS, rather than having them search willy nilly on the Web. So I was able to find news feeds appropriate for kids--here's the feeds we use http://areallydifferentplace.org/aggregator/categories
We also link to a creative writing prompt site and have the option on the blog to write Books. Continue on....N