Good luck. Nauru is not a common destination for people heading through the South Pacific since it is a very unattractive island because of the mining and the anchorage is not very good there. Also you need a pretty big boat to be able to accomodate 6 or 8 guests and their gear. A final thought, going to Banaba is pretty much exactly to windward, so even though it is not so far in terms of distance it would be a fairly rugged trip. Sounds like you might need a good-sized powerboat for this.
In South Africa doing lots of boat stuff. Departure north from Cape Town around December 15th. Arrival in the Caribbean around the beginning of February, after 5300 miles or so.