January is school holiday time, so accommodation could be a bit harder to find especially in the popular tourist spots.
January is possibly getting a bit late for the more Northern locations, especially if there's no wind, (think 40C and lots of flies.)
Lake George is fantastic when it's on, but water level is critical, and a year in advance is too long to tell what it will be like.
Here in Mandurah our speed spots rely on weed growth to be at their best, that's also unpredictable, (by me anyway).
Geraldton has some great spots, but more bump and JUMP and waves, that only rely on wind, and they seem to get plenty of it.
Not sure about renting gear or vehicles equipped to carry it.
This site has some local info on it, not sure how up to date it is.
windsurfwa.com/index.htmlCertainly be nice to catch up with you, if you come this way