If this were true I don't think Ed & Lois would be off on a cruise on the first week of school, I think rather they'd be home coaching her on what the kids were asking her at school and making sure she didn't tell them anything they didn't want her to tell.
Good point, if they have Mary K. in some kind of thrall, they wouldn't want to leave her where someone could get to her and de-program her! Wouldn't it be great if the Smarts really weren't on a cruise, but were going somewhere where Elizabeth was?