Hi Mikey!
Question #1--does your dad want to vape? Has he tried your gear? Had he expressed any interest? If he doesn't, maybe you should have a little talk with him before you go shopping. Can you take your dad to a B&M and let him play with different devices? That would be ideal, really. Vaping is hard at first even if you choose your own hardware.
A few random thoughts. Eleaf iStick is not a good device for a beginner, and I would never recommend it as a primary device--too many QC problems and it's widely inaccurate. It's a fun toy for those who own other mods they can depend on. I own it and I like it, but I don't expect it to last long. And I know all about Eleaf volts.
I also can't recommend Aspire Nautilus (it has a chromed brass chimney--not stainless steel, as advertised, and the BVC coils are stuffed with rather questionable fiberglass/ceramic non-biodegradable material that has never been tested for safety or used by any other manufacturer. But that's just me--other love the Nautilus and are not concerned. Before you buy it, I suggest you read
this thread.
I think that either a vv eGo-style battery or an MVP2 (if your dad doesn't mind the box shape) would be nice and easy to use. Add a couple of simple Kanger tanks--ProTank 2 (with an added AFC valve) or an Aerotank or Emow tank. They are reliable--but there is a learning curve and your dad will need some guidance at the beginning.
Good luck!