What topper are you going to marry up with those minis you give your nephews?
Seriously though, I ultimately believe it is the juice that has a larger impact on whether someone replaces smoking with vaping. The gear is interesting to be sure and it can hold one's interest for awhile but until one finds a flavor they really like they wont have total buy-in. Perhaps you can put together a juice program/regimen for them as well. The only way I know how to do that is to sample, sample, sample...from reputable vendors. Link them to their websites and get them looking at it. And I find encouraging them to like what I like is a mistake. I'm always amazed at what vapers like. And most of the time it isn't anything I would like. For example, SR likes spearmint. I would never make it a day with spearmint. In fact, I might throw up after five minutes. But then if SR vaped what I like he might likely have the same reaction. Yet, we were both cigarette smokers.
Good luck with your nephews. If it fails, no one will be able to blame the gear.