There’s no doubt in my mind that there will be serious job creep as well. “Oh, you’re doing her laundry? I’m really busy - could you do a load or three for us, just this once? I see you’re prepping her baby food. I’m exhausted. You wouldn’t mind making dinner for my husband and me tonight, right? Also, if you could do the dishes afterwards, I’d really appreciate it.” They’ll figure that the nanny is there anyway, so why not have her keep house for them as well.