I'd love for this to be native in the Netflix apps and to function between accounts in two different countries. Watching TV with friends and family back home would be wonderful.
I want them to develop something that works, and works very well, and then optimise it carefully.
Nice to have but non essential features should be offered in an experimental, unsupported, panel. "Try this, you might like it, but it might not work and we don't provide any support if it doesn't work".
There's a long list of software that was good, that improved to be great, and then continued to "improve" and became huge buggy laggy messes.
Then the more aged user would get the link, click on it, and it would open a browser window and inform them that this was a movie being shared with you by (your name) and to click on a link to join the viewing party. It would not be like the normal Netflix interface as you'd not be able to escape the shared viewing to browse, etc. and the title of the window would be "Shared Video: (name)" or similar in case it were bookmarked. You could go back to that shared video at anytime, similar to how Google Hangouts can reuse a hangout.
That should be simple enough in-theory for older people to get, at least as many of them that would be using it.
Unfortunately, it wouldn't work with all of the Netflix-ready devices. :( That's the problem with smart TVs and set top devices vs. browsers- you just can't innovate like that as easily.
But, it shouldn't stop Netflix from providing this feature in their browser and app versions that they have the ability to update.