Id say that it might not be such a good idea to continue bathing with your daughter, but there is absolutly nothing wrong with bathing/showering with your son.

When I was younger I remember sometimes taking showers with my dad, and in a way it was sort of a bonding experience as he was the first male I saw until I got to like camp as a kid.

Outside of the bathroom I don't see a problem with nudity with a son or daughter up to any age, if say you have a swimming pool in the back yard so thats a recreational situation that can not in any way be considered to be sexual. Long as if they decide they want to no longer be nude that you don't force them to be, and then maybe you could have you and your son wear a speedo so your not totally conservative but have the important things covered, I think its crazy when people bath their kids in swim trunks, especially if there like bathing two boys together as they don't want them to see each other, this is just the type of behavior that is messing up society.

Nudity is no suppose to be shameful, it is natural.