When my mom was deeply in the midst of Alzheimers, my daughter wanted her car. I made it clear to my daughter, that I would need to ask my mom about that. My mom had not been able to drive for a couple of years. I asked my mom about my daughter having her car. My mom's response was that it would be okay and for my daughter to "Be very, very careful!"
I believe, that even when a relative is into the deeper stages of the disease, that it's good to share as much as possible with them. We never know when doing so will get a response from them that might be like the "old" person that they were!
Thanks!