First you must be the father or this doesn't make sense and second I think odd things are nigh
I concur with JGF25. Think about it -- we're all born naked, right? Every other species of animal is "naked" and don't wear clothes -- and it's perfectly normal. We were born naked, it's natural. Nothing sexual, perfectly normal.
My sons are 15 and 17 and they do walk around in their boxers all the time. I think it is because they see their father doing it so it must be okay. To me it is like walking around in a pair of shorts. However, I would never walk around in front of them in my bra and underwear even though it looks like a bikini. Double standard there.
To answer the question about the bathroom with a glass shower door...my kids would never, ever even leave the door unlocked. They do not want me to see them naked nor do I want to see them naked. The bathroom/bedroom is the private area and if you don't lock the door then you should at least knock before you enter.
Now, looking at the flip side. Overseas, it is very common for parents and children to see each other naked. They go to beaches and eveyrbody is naked...grandma, mom, and children.
So I guess it really comes down to how you grew up. Maybe this woman grew up in a family where nudity was nothing to them. It does not have to be sexual in nature. So without knowing really the upbringing of the family no one can say it is wrong. The 24 year old boy doesn't seem to mind therefore I assume they have been a nude family all along without giving it a second thought.