I think that once the novelty wears off, unless you really want to quit, even an ecig won't do it. I found quitting to be incredibly easy with the ecig, but have to admit that after months of being analog free, the thought of a real one still sounds appealing at times. Until your dad has a real desire to be smoke free, think you may end up being disappointed. All you really can do is wait til he is ready, then have the stronger juice available. The good news is that he has been exposed to this now and knows there is an alternative that works out there, not to mention how nasty a real cig tastes now and how much nicer vaping is! Good luck.
I would not be using mine now if it was someone else's idea rather than mine. In fact, I bought my first e cig over a year and a half ago, tried it out a bit, declared it trash and put it in a drawer. I did not like the taste at all. Then last Dec. I started playing with it again every once in a while and started looking for something better. I ordered a DSE901 for $30 from Ebay and changed my mind about the concept and gradually the taste. Shortly after that, I was using it more and more, although I did still smoke cigarettes also. Finally, I reached the point where I was smoking only 1-5 cigs a day, preferring the e cig the rest of the time. Just because it's in the drawer now does not mean it will stay there. I suggest just letting your dad decide on his own to give it another try.