It is understandable why your wife's siblings and mother want to try the approach chosen. Your concerns are also justified. Unless all live nearby, have flexible work lives and very supportive spouses or partners, it will be a Herculean task to achieve.
However great our love or sense of duty to our afflicted loved one, providing 24/7 care is not for the faint hearted, it is completely exhausting, physically and mentally. The lives of not only those that provide the care are effectively put on hold, but families, grandchildren etc are also impacted.
Perhaps suggest a review date of beginning of December, or even a couple of weeks? Meanwhile be practical and proactive, research the care homes to get a better idea of what is possible.
Personally I would have laid good money that my mother, who was so terrified of going into a care home, would never settle in one. Mum took to it like a duck to water; we didn't tell her where she was going, just that we had booked her into a nice hotel for a few days, that her GP wanted her to rest and recover as she had become exhausted, it worked.
Visiting potential care homes is difficult. Begin now, see what is out there, if the family cope through this crisis, there may be a need for the info you have gleaned in the future. Good luck.
Thank you.