I guess, at least taking her on tour with an actual production is *somewhat* better than taking her on Carrie's concert tour because if something really did go wrong and Mabel needed medical attention or something, they can send the alternate on and no harm done.
But otherwise, it just seems like a really horrendous idea. They've been so needlessly anal about needing her in a routine at a young age, when at this point in her development, it largely doesn't matter, especially when you've got one parent not working and both having the flexibility of not needing to be up in the mornings. But it will matter more the older she gets, and they're planning on Carrie just dragging her around the country for nine months and leaving her with whoever. I'm no fan of Joel's, but surely she'd be better off at home in her own bed, with Dad there most of the time and maybe the grandparents or a regular nanny/babysitter in the evenings when he's at work. Hell, as expensive as childcare is, they've got the money. They could comfortably afford to put her in nursery a couple of days a week, and then she's at least getting in some engagement and socialisation with other kids. Don't think there's much chance of that when she's off on tour with Mumma. It's giving me Colleen Ballinger vibes, ngl.
Honestly, I'm surprised Joel is cool with this given how much time he's going to miss out on with his daughter. If he's already feeling like he's struggled to bond with her, this can only make it worse. I'm sorry, but if you don't feel comfortable leaving your child home with your husband, who's also their father, that's a massive red flag...not that those have ever bothered Carrie.