Well I only use our master bathroom when I'm home. I just crack it no matter who's home(of the people who live here...if someone else is here, of course I close the door. The bathroom is kind of down a hall(closet on one side vanity on the other), still in our bedroom but kind of in its own space so even if someone is in the room, they wouldn't be able to see into the toilet area.
We have one dog that has to have the door open when someone is in the bathroom. He will nudge the door with his head to see if it's open...if it's not he sits outside the door whimpering.
Mostly with DD and her bathroom if the door is cracked, he'll peak his head in, she says his name and then just keep walking down the hall. I think he thinks it's a game now. 
We have one dog that has to have the door open when someone is in the bathroom. He will nudge the door with his head to see if it's open...if it's not he sits outside the door whimpering.
Mostly with DD and her bathroom if the door is cracked, he'll peak his head in, she says his name and then just keep walking down the hall. I think he thinks it's a game now. 
Seriously? Why?

I remember watching my little son's chubby fingers sneaking in under the door...he learned to cope with the separation - maybe your cats could too. 