Well, the astrological and psychological slant is that Lana's A Cancer, and Cancer is the sign of the home and of parenting. Plus she's in early middle age and grew up listening to another Cancer, Carly Simon, who made several great albums in the 70s which focused on her family, children, her own childhood, and her husband (James Taylor) as much as they did on her lovers and love life. Some of these were really beautiful and reached a sort of universal lyricism so that almost anyone, anywhere, could and can relate to them ('The Carter Family,' 'Grownup,' 'Forever My Love,' 'Boys in the Trees,' 'Sons of Summer,' 'His Friends Are More Than Fond of Robin,' and her acknowledgement of a romantic lesbian relationship, 'Libby.') If you give these tracks a listen, you might see a little influence on Lana's more recent work. and most Simon songs are piano-based.
As I've mentioned here before, I've observed that when writers start having children, or get married, they often lose a lot of angst, temporarily or permanently, and start writing sometimes sappy declarations of parenthood, happiness, and marital bliss. Tori Amos did this with 'Jackie's Strength,' about her wedding day, and the saccharine 'Ribbons Undone,' about her young daughter. Kate Bush impressed no one with 'Bertie,' about her young son. Male songwriters have done this too, if, in my experience, less often. The songrwriter want to write about and share what's taken over their lives, but they don't realize almost every parent loves their kid, is impressed by her or him, or thinks them special, and this is not necessarily what their fanbase is waiting for. Kenny Loggins of Loggins & Messina wrote 'Danny's Song' about his young son early in their career, and it became a huge radio classic in its day, and it's not sappy, but touching.
Personally, I don't think 'Dance 'Til We Die' is predominantly about children or the desire for children; the overall point is, as I see it, just reject the bullshit that is no doubt going to keep coming and keep living to the fullest until your last breath, just as 'For Free' is not about performing, but about humility and being humbled. That's clear in the grimmer Mitchell original, which doesn't add the happy little fillips at the end of the lines the way Lana's half-baked version did. It's as if Lana could not bear to really sing the song as written and had to lighten it up so it could have something resembling a happy ending. Had she sung it as Mitchell did, it would have been the perfect compliment to 'Yosemite.'
I, too, worry that we might be getting more 'Sweet Carolinas' with 'The Grants,' though I didn't mind 'SC' but don't want to see much more of. As you both said, it's a personal song, it's Lana's song to a beloved family member, and she could have saved it for some kind of giant career retrospective full of unreleased rarities, etc., which is no doubt bound to come, or sung it at a birthday party. I certainly didn't mind the family romance (Freud) outlined in 'WFWF.'
But who knows? 'The Grants' might be some sort of satirical masterpiece, and musically, it could go anywhere. Since BOZ and others have us primed to expect some really unusual instrumentation, songwriting, and production on the new record, that's what I'm anticipating, with some hesitancy.
I'm still waiting for Trip Hop Lana to show her face again. My favorite two songs of this year are the Trip Hop 'If I Were A Butterfly' and 'Thunder Sound' by Rayland Baxter.