Language Islands

If I build up lots of language islands as a separate course.  This would be vocabulary and sentence to do with certain topics then we could have really nice talks about the those topics.
I'm just thinking it could be about animals.  Lots of words about animals that are useful.  All put onto the website.  Use the five sentence thing to learn them.  
Then they come to the lesson prepared to chat about those things.
It really does need preparation by them though.  it doesn't work otherwise.  Does it?

Could I prepare them in the lesson?  e.g. teach them the animals?