I am inclined not to narrow the definition of nuclear family to eliminate "granny" from the mix.
Changing the goalposts because you don't like the outcome? Words have meanings in the real world, and those two terms 'nuclear' (first used with the word 'family' in 1947 to describe the emerging post war social situations - so hardly as old as America) and 'extended' have definite meanings, and nuclear specifically refers to kicking granny to the curb, or the retirement home, or maybe granny is cruising America in a motor home. Whatever she is doing, she's not doing it as part of the 'family'. "Nuclear" refers to TWO (not more) generations in the same house, parents and their own kids, while "extended" includes other generations, or other relatives not of immediate blood line also living in the home. So when JM built a granny/mother-in-law unit, that was exactly what an extended family would do (as common in that time).
In fact the nuclear family is one very prominent example of recent failed social engineering.
Women and kids working in the household's business
And that's bad exactly how? As soon as my kids were old enough they were working for us. Either by going to the libarary with me and pulling research and makin' copies, or at the club my ex ran, where we asked them: "So, you want to be in show biz?" "Yeah!" "OK, here's a broom, sweep the stage.", they would sweep, take tickets, organize tickets, clean up, entertain the band, babysit for the bands baby, whatever it takes, whatever the party calls for. That's how you learn to work.