That should be possible.
Some considerations:
- With 3-4 parallel streams, you should also keep your home network as possible limiting factor in mind.
- To streamline things… consider to create mp4/h264 versions of the videos from your DVDs with AAC/AC3 audio (e.g. using Handbrake).
With 6 children… you might want to look into setting up a “Plex Home” and give your children “managed users” so you can control what they see (if they are young you might not want to share your horror collection or movies rated R with them)
https://support.plex.tv/articles/categories/features/plex-home/ (related support articles also have a nice Simpsons-themed example)
As for 4K… that’s on a totally different page and might be too much for your future NAS (at least when it comes to playing more than 1 stream).
