I'm going to have to second this. I've gotten my older family members PCs in the past and it's always turned into a major headache for me. Your best bet is one of two solutions:
1) Apple everything: Macintosh based computers, Ipad tablets, iphones (if they are cellular users), and apple TV streaming devices. While many rip on apple (including me. I was a mac fan in the apple 2/ mac 2 era, but got burned in the shift to OS X) once your completely in everything just works. If they need help applecare or the apple stores are there to assist or you can use something like Teamviewer to log in remotely.
2) Google everything: Chrometop based computers and Chromebook laptops, Android tablets and phones, and finally Nexus players for TV's and stereos. Much like the apple ecosystem Google equipment works well together. Maybe not as much at the local level, but once you tie them to your Google account everything is tied nicely through web services. Unlike PC (and even apple equipment) Chromebooks and Chrometops are immune to viruses as each time you hard boot they get a fresh OS from ROM. Use their existing PC to push their music and photos to Google Music and Photos.
As for the printer get a networked hard wired multi-function printer. I've found issues with WiFi printers including poor sleep states and difficulty getting them to resync to the WiFi after a power event. A hard wired printer is more reliable. By hard wiring it you make sure everything is in one location. Cable modem, WiFi router, and printer. Tie it all into the same surge protector and if anything goes wrong your mom and dad just need to know to turn off the surge strip for a minute then kick it back on.
As for your dad's 3tb drive I'm not sure what he would be storing on that. In the Apple ecosystem he could either just attach it as a external to what ever mac he chooses to use, link it to his router and use it as network attached storage, or plug it into a real NAS box like a synology. On the Google ecosystem you are limited to just external storage. You probably could push the files to google docs if he wants to pay for more storage (unless it's all photos and music then the basic account would probably do) and just hang on to the 3TB drive as an emergency backup.
Hope this helps. While windows is the primary OS, I'm finding older relatives who are less technical are better served by other technologies. Especially since these "Indian tech support scams" are becoming more commonplace. I've had to remind all of my relatives that "Microsoft will never call you". The ones who have Macs and Chromebooks usually just hang up because they already understand that Microsoft wouldn't provide support for their device.