Your dad’s gonna be just fine.
He has a Pilot license, has used a simulator in the past, and having an iPad and a laptop means he is aquainted with modern technology.
He’ll find his way around MSFS in no time.
Also he’s likely just the right age for Flight Simulators. (I don’t know his age obviously). You’ll find a lot of people in this genre who are at it for decades… In one forum I partake in, we have an MSFS pilot in his Nineties and many pensioneers…
MSFS is actually pretty complete package, so my advice would be to keep it simple.
MSFS has the whole world, 35.000 airports, 40 aircraft, a weather system, AI Air Traffic Operators, a basic flight planner and can be used solely with a Xbox controller.
The Xbox version has two significant advantages: MSFS updates on it’s own and you cannot mess up the program, like you can as a PC user 
Whether your dad even wants to use external apps, websites or additional content in his first months of flying in MSFS is not set in stone.
A couple of bookmarks to useful websites and web-applications is the most he might want in the beginning.
Seriously.
Subscribing to some useful Youtube channels is also good and reading this forum.
Three aspects however come to mind.
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MSFS has bugs. Some are minor nuisances, some more annoying. Your dad will encounter bugs with the program.
Good thing is, Microsoft is constantly working on MSFS, upgrading things and what not.
So patience is key here as a user when something in the program is simply not working 100% as expected, until they get around to fixing things for us.
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Once you are inside MSFS, your dad will want to install the free extra content he can find in the Marketplace. Mainly the G1000NXi Avionic system and all of the free World Updates.
Then he will want to look at the Assistance Options and since he knows how to fly a plane, turn off most of them 
Most of them are not meant for somebody with a Pilot’s license, that’s for sure.
(Current bug : they get reset to EASY on their own, so check before each flight…)
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Peripherals
A Joystick or Yoke will have to be Xbox compatible. Not many choices, this is the complete list :
I only know the Thrustmaster Hotas One Xbox version and the Turtle Beach Velocity One. There’s propably more, but i use an simple Xbox controller to fly, so not much advice to give.
Current bug: sensitivity settings of Joystick or Yoke are not saved. So either use default or set them every time a new.
Microsoft knows and is hopefully fixing it in an update.
You dad’s propably gonna have a use for the Xbox controller that comes with the console.
For the drone camera or navigating the cockpit if the mouse fails (ahem, another bug that sometimes happens)
This is very useful if you don’t wanna constantly change AA batteries for the controller :
Keyboard and Mouse
You definitely want a Keyboard and while your at it a mouse.
You have to enter stuff when planning a flight and you can use the buttons on the keyboard to trigger all kind of buttons in the cockpit.
Any regular Windows or PC compatible keyboard/mouse is fine. They can be very cheap, like from 20 bucks or so on Amazon as a set.
If it’s with a cable, then of course it depends how far the distance is to the Xbox.
If it’s wireless, it needs to have a little USB Stick with it for the Bluetooth transmission. And it means you gonna have to recharge them every now and then or change batteries.
Current: Bug: Sometines the Mouse movement just stops in MSFS until the program is restarted.
Microsoft knows this and is hopefully fixing it eventually.
Another advice: forget all those flight school tutorials and bush trips and so on, just start flying. The tutorials tend to be buggy and your dad knows how to fly already.
here’s a flight planning tutorial to get him started on how to set up a flight in MSFS. (Simhanger has a number of great tutorials)