As what Johnnyaxxe mentioned, convenience is key.

For someone used to analog cigarettes a big issue would be convenience. You can buy a pack of cigs with ease anytime your out of cigs or forgot or misplaced your pack, and borrowing a lighter might be the easiest thing to borrow in the world!

So with that said, without will power to switch to electronic cigarettes a smoker would be discourged to make the switch immediately if faced with a situation of not being able to vape because your all out on batteries.

A common mistake that faces alot of people who are trying to convert or trying to help some one convert is trying to skip steps to minimize the cost by buying an advanced setup that can accommodate advanced vaping styles in case they wanted to catch up with the vaping trends without reinvesting in a new setup. This is an issue because vaping have evolved in the recent years towards a different nicotine delivery experience rather than mimicking a cigarette.

I would suggest a setup of 2-3 vape pen batteries depending on how much he used to smoke, preferably something like the innokin CLK that can be charged by a micro usb.

I don't know about what atomizer to pair the batteries with as I only tried the CE4 atomizer when I first started using a vape pen.

If any one can recommend a more discreet setup please do so as for someone in your dad's age demographic might be discouraged to use a flashy setup; the more discreet the better.

And for the eliquid you need to understand your dad smoking habits, a person who enjoys smoking the most while drinking coffee will enjoy different flavor profiles than someone who enjoy smoking while sipping on his favorite spirit.

The last point you need to have in mind when selecting a nicotine level don't go below 18mg, the idea is getting rid of the cigarettes carcinogens and not lowering down the nicotine intake, that comes at a later stage.