Well done - it is hard.
I removed and hid my mum's car keys, and refused to tell my OH or kids where they were so they couldn't be tricked into getting something out of the car for her. Once in her sheltered extra care flat she asked about a mobility scooter, but for the same reasons she wasn't safe to drive I didn't feel she would be safe.
In fact I felt she would be more likely to injure someone than driving as she had lost spatial awareness and the ability to 'see' what she wasn't expecting, so might be on pavement and run over a child or would cross road without seeing a lorry bearing down.
She was also no longer safe to cross busy roads on foot. Spatial awareness and inability to 'see' despite passing an eye test are not apparent to others either, who think the person appears OK.