Password protect a folder?

I have searched around and can not find anything specific to this question. I am currently using a BDP-S570.
Can you password protect a folder for a certain device? Or only show certain folders to certain devices?
This is why I ask, I have an 8 year old son and may get him something like a WD Live Plus box or another Sony Blu-ray player for his room so he has access to his movies. I have the movies split out into 4 different folders (i.e. Baby Movies, Kid Movies, PG-13 Movies, & R-Rated Movies). Obviously my concern is him stumbling upon Hot Tub Time Machine or something he shouldn't be watching while being a curious kid. I would only want his device to have access to Baby Movies for him and his little brother to watch together as well as the Kid Movies.
The password protection may be related to the Sony player and not Serviio, but I am hoping someone will say you can limit what folders certain devices can have access too.
Can you password protect a folder for a certain device? Or only show certain folders to certain devices?
This is why I ask, I have an 8 year old son and may get him something like a WD Live Plus box or another Sony Blu-ray player for his room so he has access to his movies. I have the movies split out into 4 different folders (i.e. Baby Movies, Kid Movies, PG-13 Movies, & R-Rated Movies). Obviously my concern is him stumbling upon Hot Tub Time Machine or something he shouldn't be watching while being a curious kid. I would only want his device to have access to Baby Movies for him and his little brother to watch together as well as the Kid Movies.
The password protection may be related to the Sony player and not Serviio, but I am hoping someone will say you can limit what folders certain devices can have access too.