Honestly, I still think you're going about this the wrong way.
Your solution is privileging FreeNAS, but I'm not sure what you want out of FreeNAS. It sounds like you think we're getting caught up on the Windows bit; this is incorrect. We can't figure out why you want to use FreeNAS
at all in the first place.
From your posts, I see the following explicit requirements:
- One computer
- Provides NAS capabilities
- Runs Windows programs/flash
Of note, there are no requirements to provide data security (over and above a possible desire to do mirroring sometime in the future). I too would recommend running Windows and being done with it. Windows will provide all your NAS capabilities, Windows can do software mirroring of drives for redundancy, it will run Plex and pretty much any other program you need. Windows also has a lot of very user friendly programs that can be used to control your little one's computer user time, website visits, etc.
If Windows is not your thing, than maybe Linux with WINE would do (depending on the program). You also can also do disk mirroring, run Plex, etc.