My parents don't drive but need their vehicle. How do we make it work?

My mother is mobility challenged. She normally gets around with a walker in the house, but needs a wheel chair when out. My dad just entered hospice and had to surrender his drivers license.

Since neither of them has a valid drivers license anymore, they cannot register their vehicle. It is set up so that my mom can get in and out with relative ease. She needs it to get to and from the Clinic which is about an hour drive.

There are people willing to transport her, but she cannot get into or out of their vehicles easily. How can we keep the vehicle licensed and insured so someone else may drive it?

Both my sister and I are out of state. It is a 5 hour drive for me to get to their home, and my sister is about 14 hours drive time away. I want to purchase the vehicle, license it here and let them keep it. My sister isn’t happy with me doing that.