I was in the same shoes as MomInAlberta - 4 kids and too many activities and no time, but what's wrong with taking your baby in the shower with you in the morning for a quick scrub up if you're short on time? Or a 3 minute bath before bed? That's what I used to do with my stinky little ones.
I can't stand stinkiness either so I would have a problem if I were you DeeDee. Are you still going to be washing your nephew up every morning when he's 3 or 4? I'm afraid I would have to find a nice way to bring up the subject with your SIL if I were you. You can say it nicely but honestly if you are gentle.