My husband has never showered with our kids but when they were little on occasion they would take a bath and color on the walls, washable crayons work great for this, not the soap ones. Anyways, I don't think I have an age where my kids can't shower with me it just naturally doesn't happen any more. My 4 year old still like to, but my 7 year old son wouldn't think of it, of course you have to drag him to the shower these days and the baby still likes to.
I must say that my teens, will walk in the bathroom as I am getting ready to shower and not blink twice as I stand there naked, used to drive me crazy, But not anymore. My husband is also carefull about changing in front of the little ones cause they have a habit (when babies) of thinking his "pickle" is some kind of horn to toot. I always find it
, he doesn't.
I guess it's up to the dynamics of the household, I do think that at a certain point parents of the opposite sex should stop showering or bathing with their kids, but mainly cause society can twist even the simplest things and turn around and use them against us.