As long as you aren't paying the CFI to fly you to the bahamas, it isn't a Charter. If you're just paying him for instruction, you're fine. You will, of course, need a 100 hour since you are paying him for instruction. Also, keep in mind he can only instruct for 8 hours in any given 24 hour period. I can see where this could raise questions, but if he is legitimately giving flight instruction then it's legal, regardless who owns the plane. (If I'm wrong please quote me the regs...I can't find anything that says this would be an illegal charter.)